Module build failed (from ./node_modules/mini-css-extract-plugin/dist/loader.js): ReferenceError: document is not defined

Ok, So basically We use webpack to bundle our resources before deployment. However, now we want to also bundle our sass files through webpack is it simplifies our build process.it was going well, but now bundle.js is too big to deploy on production so I wanted to split bundle.js and styling files. I don’t much know about plugins and all ,so I searched a little bit and found that mini-css-extract-plugin lets me split style files into a new file. So I went and tweaked the web-pack.config file according to the docs of mini-css-extract-plugin but I am getting so many errors. Can somebody guide me to split styles file and extract it from bundle.js?

error :

ERROR in ./node_modules/normalize.css/normalize.css
Module build failed (from ./node_modules/mini-css-extract-plugin/dist/loader.js):
ReferenceError: document is not defined
    at insertStyleElement (D:ReactJs-ProjectsExpensify-appnode_modulesstyle-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulescss-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulessass-loaderlibloader.js!D:ReactJs-ProjectsExpensify-appnode_modulesnormalize.cssnormalize.css:309:15)    at addStyle (D:ReactJs-ProjectsExpensify-appnode_modulesstyle-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulescss-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulessass-loaderlibloader.js!D:ReactJs-ProjectsExpensify-appnode_modulesnormalize.cssnormalize.css:424:13)
    at modulesToDom (D:ReactJs-ProjectsExpensify-appnode_modulesstyle-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulescss-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulessass-loaderlibloader.js!D:ReactJs-ProjectsExpensify-appnode_modulesnormalize.cssnormalize.css:297:18)      
    at module.exports.module.exports (D:ReactJs-ProjectsExpensify-appnode_modulesstyle-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulescss-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulessass-loaderlibloader.js!D:ReactJs-ProjectsExpensify-appnode_modulesnormalize.cssnormalize.css:455:25)
    at Object.<anonymous> (D:ReactJs-ProjectsExpensify-appnode_modulesstyle-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulescss-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulessass-loaderlibloader.js!D:ReactJs-ProjectsExpensify-appnode_modulesnormalize.cssnormalize.css:206:14)    at __webpack_require__ (D:ReactJs-ProjectsExpensify-appnode_modulesstyle-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulescss-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulessass-loaderlibloader.js!D:ReactJs-ProjectsExpensify-appnode_modulesnormalize.cssnormalize.css:21:30)    at D:ReactJs-ProjectsExpensify-appnode_modulesstyle-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulescss-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulessass-loaderlibloader.js!D:ReactJs-ProjectsExpensify-appnode_modulesnormalize.cssnormalize.css:85:18
    at Object.<anonymous> (D:ReactJs-ProjectsExpensify-appnode_modulesstyle-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulescss-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulessass-loaderlibloader.js!D:ReactJs-ProjectsExpensify-appnode_modulesnormalize.cssnormalize.css:88:10) 
    at Module._compile (D:ReactJs-ProjectsExpensify-appnode_modulesv8-compile-cachev8-compile-cache.js:194:30)
    at evalModuleCode (D:ReactJs-ProjectsExpensify-appnode_modulesmini-css-extract-plugindistloader.js:61:10)
    at D:ReactJs-ProjectsExpensify-appnode_modulesmini-css-extract-plugindistloader.js:166:21
    at D:ReactJs-ProjectsExpensify-appnode_moduleswebpacklibCompiler.js:343:11
    at D:ReactJs-ProjectsExpensify-appnode_moduleswebpacklibCompiler.js:681:15
    at AsyncSeriesHook.eval [as callAsync] (eval at create (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHookCodeFactory.js:33:10), <anonymous>:15:1)
    at AsyncSeriesHook.lazyCompileHook (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHook.js:154:20)
    at D:ReactJs-ProjectsExpensify-appnode_moduleswebpacklibCompiler.js:678:31
    at AsyncSeriesHook.eval [as callAsync] (eval at create (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHookCodeFactory.js:33:10), <anonymous>:6:1)    at AsyncSeriesHook.lazyCompileHook (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHook.js:154:20)
    at D:ReactJs-ProjectsExpensify-appnode_moduleswebpacklibCompilation.js:1423:35
    at AsyncSeriesHook.eval [as callAsync] (eval at create (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHookCodeFactory.js:33:10), <anonymous>:6:1)    at AsyncSeriesHook.lazyCompileHook (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHook.js:154:20)
    at D:ReactJs-ProjectsExpensify-appnode_moduleswebpacklibCompilation.js:1414:32
    at eval (eval at create (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHookCodeFactory.js:33:10), <anonymous>:11:1)
    at D:ReactJs-ProjectsExpensify-appnode_modulesterser-webpack-plugindistindex.js:321:9
    at TaskRunner.run (D:ReactJs-ProjectsExpensify-appnode_modulesterser-webpack-plugindistTaskRunner.js:48:7)
    at TerserPlugin.optimizeFn (D:ReactJs-ProjectsExpensify-appnode_modulesterser-webpack-plugindistindex.js:227:18)
    at AsyncSeriesHook.eval [as callAsync] (eval at create (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHookCodeFactory.js:33:10), <anonymous>:7:1)    at AsyncSeriesHook.lazyCompileHook (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHook.js:154:20)
    at D:ReactJs-ProjectsExpensify-appnode_moduleswebpacklibCompilation.js:1409:36
    at AsyncSeriesHook.eval [as callAsync] (eval at create (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHookCodeFactory.js:33:10), <anonymous>:6:1)    at AsyncSeriesHook.lazyCompileHook (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHook.js:154:20)
    at D:ReactJs-ProjectsExpensify-appnode_moduleswebpacklibCompilation.js:1405:32
    at AsyncSeriesHook.eval [as callAsync] (eval at create (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHookCodeFactory.js:33:10), <anonymous>:6:1)    at AsyncSeriesHook.lazyCompileHook (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHook.js:154:20)
    at Compilation.seal (D:ReactJs-ProjectsExpensify-appnode_moduleswebpacklibCompilation.js:1342:27)
    at D:ReactJs-ProjectsExpensify-appnode_moduleswebpacklibCompiler.js:675:18
 @ ./src/app.js 10:0-37

ERROR in ./node_modules/react-dates/lib/css/_datepicker.css
Module build failed (from ./node_modules/mini-css-extract-plugin/dist/loader.js):
ReferenceError: document is not defined
    at insertStyleElement (D:ReactJs-ProjectsExpensify-appnode_modulesstyle-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulescss-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulessass-loaderlibloader.js!D:ReactJs-ProjectsExpensify-appnode_modulesreact-dateslibcss_datepicker.css:309:15)
    at addStyle (D:ReactJs-ProjectsExpensify-appnode_modulesstyle-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulescss-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulessass-loaderlibloader.js!D:ReactJs-ProjectsExpensify-appnode_modulesreact-dateslibcss_datepicker.css:424:13)  
    at modulesToDom (D:ReactJs-ProjectsExpensify-appnode_modulesstyle-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulescss-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulessass-loaderlibloader.js!D:ReactJs-ProjectsExpensify-appnode_modulesreact-dateslibcss_datepicker.css:297:18)
    at module.exports.module.exports (D:ReactJs-ProjectsExpensify-appnode_modulesstyle-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulescss-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulessass-loaderlibloader.js!D:ReactJs-ProjectsExpensify-appnode_modulesreact-dateslibcss_datepicker.css:455:25)
    at Object.<anonymous> (D:ReactJs-ProjectsExpensify-appnode_modulesstyle-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulescss-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulessass-loaderlibloader.js!D:ReactJs-ProjectsExpensify-appnode_modulesreact-dateslibcss_datepicker.css:206:14)
    at __webpack_require__ (D:ReactJs-ProjectsExpensify-appnode_modulesstyle-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulescss-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulessass-loaderlibloader.js!D:ReactJs-ProjectsExpensify-appnode_modulesreact-dateslibcss_datepicker.css:21:30)
    at D:ReactJs-ProjectsExpensify-appnode_modulesstyle-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulescss-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulessass-loaderlibloader.js!D:ReactJs-ProjectsExpensify-appnode_modulesreact-dateslibcss_datepicker.css:85:18
    at Object.<anonymous> (D:ReactJs-ProjectsExpensify-appnode_modulesstyle-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulescss-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulessass-loaderlibloader.js!D:ReactJs-ProjectsExpensify-appnode_modulesreact-dateslibcss_datepicker.css:88:10)
    at Module._compile (D:ReactJs-ProjectsExpensify-appnode_modulesv8-compile-cachev8-compile-cache.js:194:30)
    at evalModuleCode (D:ReactJs-ProjectsExpensify-appnode_modulesmini-css-extract-plugindistloader.js:61:10)
    at D:ReactJs-ProjectsExpensify-appnode_modulesmini-css-extract-plugindistloader.js:166:21
    at D:ReactJs-ProjectsExpensify-appnode_moduleswebpacklibCompiler.js:343:11
    at D:ReactJs-ProjectsExpensify-appnode_moduleswebpacklibCompiler.js:681:15
    at AsyncSeriesHook.eval [as callAsync] (eval at create (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHookCodeFactory.js:33:10), <anonymous>:15:1)
    at AsyncSeriesHook.lazyCompileHook (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHook.js:154:20)
    at D:ReactJs-ProjectsExpensify-appnode_moduleswebpacklibCompiler.js:678:31
    at AsyncSeriesHook.eval [as callAsync] (eval at create (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHookCodeFactory.js:33:10), <anonymous>:6:1)    at AsyncSeriesHook.lazyCompileHook (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHook.js:154:20)
    at D:ReactJs-ProjectsExpensify-appnode_moduleswebpacklibCompilation.js:1423:35
    at AsyncSeriesHook.eval [as callAsync] (eval at create (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHookCodeFactory.js:33:10), <anonymous>:6:1)    at AsyncSeriesHook.lazyCompileHook (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHook.js:154:20)
    at D:ReactJs-ProjectsExpensify-appnode_moduleswebpacklibCompilation.js:1414:32
    at eval (eval at create (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHookCodeFactory.js:33:10), <anonymous>:11:1)
    at D:ReactJs-ProjectsExpensify-appnode_modulesterser-webpack-plugindistindex.js:321:9
    at TaskRunner.run (D:ReactJs-ProjectsExpensify-appnode_modulesterser-webpack-plugindistTaskRunner.js:48:7)
    at TerserPlugin.optimizeFn (D:ReactJs-ProjectsExpensify-appnode_modulesterser-webpack-plugindistindex.js:227:18)
    at AsyncSeriesHook.eval [as callAsync] (eval at create (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHookCodeFactory.js:33:10), <anonymous>:7:1)    at AsyncSeriesHook.lazyCompileHook (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHook.js:154:20)
    at D:ReactJs-ProjectsExpensify-appnode_moduleswebpacklibCompilation.js:1409:36
    at AsyncSeriesHook.eval [as callAsync] (eval at create (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHookCodeFactory.js:33:10), <anonymous>:6:1)    at AsyncSeriesHook.lazyCompileHook (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHook.js:154:20)
    at D:ReactJs-ProjectsExpensify-appnode_moduleswebpacklibCompilation.js:1405:32
    at AsyncSeriesHook.eval [as callAsync] (eval at create (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHookCodeFactory.js:33:10), <anonymous>:6:1)    at AsyncSeriesHook.lazyCompileHook (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHook.js:154:20)
    at Compilation.seal (D:ReactJs-ProjectsExpensify-appnode_moduleswebpacklibCompilation.js:1342:27)
    at D:ReactJs-ProjectsExpensify-appnode_moduleswebpacklibCompiler.js:675:18
 @ ./src/components/ExpenseForm.js 27:0-45
 @ ./src/components/AddExpensePage.js
 @ ./src/routers/AppRouter.js
 @ ./src/app.js

ERROR in ./src/styles/styles.scss
Module build failed (from ./node_modules/mini-css-extract-plugin/dist/loader.js):
ReferenceError: document is not defined
    at insertStyleElement (D:ReactJs-ProjectsExpensify-appnode_modulesstyle-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulescss-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulessass-loaderlibloader.js!D:ReactJs-ProjectsExpensify-appsrcstylesstyles.scss:309:15)
    at addStyle (D:ReactJs-ProjectsExpensify-appnode_modulesstyle-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulescss-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulessass-loaderlibloader.js!D:ReactJs-ProjectsExpensify-appsrcstylesstyles.scss:424:13)
    at modulesToDom (D:ReactJs-ProjectsExpensify-appnode_modulesstyle-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulescss-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulessass-loaderlibloader.js!D:ReactJs-ProjectsExpensify-appsrcstylesstyles.scss:297:18)
    at module.exports.module.exports (D:ReactJs-ProjectsExpensify-appnode_modulesstyle-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulescss-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulessass-loaderlibloader.js!D:ReactJs-ProjectsExpensify-appsrcstylesstyles.scss:455:25)       
    at Object.<anonymous> (D:ReactJs-ProjectsExpensify-appnode_modulesstyle-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulescss-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulessass-loaderlibloader.js!D:ReactJs-ProjectsExpensify-appsrcstylesstyles.scss:206:14)
    at __webpack_require__ (D:ReactJs-ProjectsExpensify-appnode_modulesstyle-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulescss-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulessass-loaderlibloader.js!D:ReactJs-ProjectsExpensify-appsrcstylesstyles.scss:21:30)
    at D:ReactJs-ProjectsExpensify-appnode_modulesstyle-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulescss-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulessass-loaderlibloader.js!D:ReactJs-ProjectsExpensify-appsrcstylesstyles.scss:85:18
    at Object.<anonymous> (D:ReactJs-ProjectsExpensify-appnode_modulesstyle-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulescss-loaderdistcjs.js!D:ReactJs-ProjectsExpensify-appnode_modulessass-loaderlibloader.js!D:ReactJs-ProjectsExpensify-appsrcstylesstyles.scss:88:10)
    at Module._compile (D:ReactJs-ProjectsExpensify-appnode_modulesv8-compile-cachev8-compile-cache.js:194:30)
    at evalModuleCode (D:ReactJs-ProjectsExpensify-appnode_modulesmini-css-extract-plugindistloader.js:61:10)
    at D:ReactJs-ProjectsExpensify-appnode_modulesmini-css-extract-plugindistloader.js:166:21
    at D:ReactJs-ProjectsExpensify-appnode_moduleswebpacklibCompiler.js:343:11
    at D:ReactJs-ProjectsExpensify-appnode_moduleswebpacklibCompiler.js:681:15
    at AsyncSeriesHook.eval [as callAsync] (eval at create (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHookCodeFactory.js:33:10), <anonymous>:15:1)
    at AsyncSeriesHook.lazyCompileHook (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHook.js:154:20)
    at D:ReactJs-ProjectsExpensify-appnode_moduleswebpacklibCompiler.js:678:31
    at AsyncSeriesHook.eval [as callAsync] (eval at create (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHookCodeFactory.js:33:10), <anonymous>:6:1)    at AsyncSeriesHook.lazyCompileHook (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHook.js:154:20)
    at D:ReactJs-ProjectsExpensify-appnode_moduleswebpacklibCompilation.js:1423:35
    at AsyncSeriesHook.eval [as callAsync] (eval at create (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHookCodeFactory.js:33:10), <anonymous>:6:1)    at AsyncSeriesHook.lazyCompileHook (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHook.js:154:20)
    at D:ReactJs-ProjectsExpensify-appnode_moduleswebpacklibCompilation.js:1414:32
    at eval (eval at create (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHookCodeFactory.js:33:10), <anonymous>:11:1)
    at D:ReactJs-ProjectsExpensify-appnode_modulesterser-webpack-plugindistindex.js:321:9
    at TaskRunner.run (D:ReactJs-ProjectsExpensify-appnode_modulesterser-webpack-plugindistTaskRunner.js:48:7)
    at TerserPlugin.optimizeFn (D:ReactJs-ProjectsExpensify-appnode_modulesterser-webpack-plugindistindex.js:227:18)
    at AsyncSeriesHook.eval [as callAsync] (eval at create (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHookCodeFactory.js:33:10), <anonymous>:7:1)    at AsyncSeriesHook.lazyCompileHook (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHook.js:154:20)
    at D:ReactJs-ProjectsExpensify-appnode_moduleswebpacklibCompilation.js:1409:36
    at AsyncSeriesHook.eval [as callAsync] (eval at create (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHookCodeFactory.js:33:10), <anonymous>:6:1)    at AsyncSeriesHook.lazyCompileHook (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHook.js:154:20)
    at D:ReactJs-ProjectsExpensify-appnode_moduleswebpacklibCompilation.js:1405:32
    at AsyncSeriesHook.eval [as callAsync] (eval at create (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHookCodeFactory.js:33:10), <anonymous>:6:1)    at AsyncSeriesHook.lazyCompileHook (D:ReactJs-ProjectsExpensify-appnode_modulestapablelibHook.js:154:20)
    at Compilation.seal (D:ReactJs-ProjectsExpensify-appnode_moduleswebpacklibCompilation.js:1342:27)
    at D:ReactJs-ProjectsExpensify-appnode_moduleswebpacklibCompiler.js:675:18
 @ ./src/app.js 11:0-30

webpack.config.js :

const path = require("path");
//const ExtractTextPlugin = require("extract-text-webpack-plugin");
const MiniCssExtractPlugin = require("mini-css-extract-plugin");

module.exports = env => {
    const isProduction = env === "production";
    //const CSSExtract = new ExtractTextPlugin("styles.css");

    console.log("env", env);
    return {
        entry: "./src/app.js",
        output: {
            path: path.join(__dirname, "public"),
            filename: "bundle.js",
        },
        module: {
            rules: [
                {
                    loader: "babel-loader",
                    test: /.js$/,
                    exclude: /node_modules/,
                },
                {
                    test: /.s?css$/,
                    use: [
                        {
                            loader: MiniCssExtractPlugin.loader,
                            options: {
                                publicPath: path.join(__dirname, "public"),
                            },
                        },
                        "style-loader",
                        "css-loader", 
                        "sass-loader", 
                    ],
                },
            ],
        },
        plugins: [
            new MiniCssExtractPlugin({
                filename: "styles.css",
            }),
        ],
        // plugins: [CSSExtract],
        devtool: isProduction ? "source-map" : "cheap-module-eval-source-map", 

        devServer: {
            contentBase: path.join(__dirname, "public"),
            historyApiFallback: true,
        },
    };
};

package.json :

{
    "name": "expensify-app",
    "version": "1.0.0",
    "main": "index.js",
    "author": "Viral Thaker",
    "license": "MIT",
    "scripts": {
        "serve": "live-server public/",
        "build:dev": "webpack",
        "build:prod": "webpack -p --env production",
        "dev-server": "webpack-dev-server",
        "start": "npm run dev-server",
        "test": "jest"
    },
    "dependencies": {
        "babel-cli": "^6.26.0",
        "babel-core": "^6.26.3",
        "babel-loader": "^8.1.0",
        "babel-plugin-transform-class-properties": "^6.24.1",
        "babel-plugin-transform-object-rest-spread": "^6.26.0",
        "css-loader": "^4.0.0",
        "jest": "^26.4.1",
        "live-server": "^1.2.1",
        "moment": "^2.27.0",
        "node-sass": "^4.14.1",
        "normalize.css": "^8.0.1",
        "react": "^16.13.1",
        "react-addons-shallow-compare": "^15.6.2",
        "react-dates": "^21.8.0",
        "react-dom": "^16.13.1",
        "react-modal": "^3.11.2",
        "react-redux": "^7.2.1",
        "react-router-dom": "^5.2.0",
        "redux": "^4.0.5",
        "sass-loader": "^6.0.6",
        "style-loader": "^1.2.1",
        "uuid": "^8.3.0",
        "validator": "^13.1.1"
    },
    "devDependencies": {
        "@babel/core": "^7.10.5",
        "@babel/preset-env": "^7.10.4",
        "@babel/preset-react": "^7.10.4",
        "extract-text-webpack-plugin": "^4.0.0-beta.0",
        "mini-css-extract-plugin": "^0.10.0",
        "webpack": "^4.44.1",
        "webpack-cli": "^3.3.12",
        "webpack-dev-server": "^3.11.0"
    }
}

Answer

As Camilo suggested there was this "style-loader" which was somehow conflicting to the plugin but anyway as I am separating CSS files I don’t need inline CSS so I completely removed it from the loader and the error was completely gone and it gave me a new build with separate CSS file

Anyone, having the same problem in future just look for your loader whether its conflicting