webpack.config.js

const path = require('path');
const MiniCssExtractPlugin = require("mini-css-extract-plugin"); 
 //Explanation about MiniCSSExtract Plugin https://github.com/webpack-contrib/mini-css-extract-plugin/issues/42

module.exports = {
    entry: {
        index: ['babel-polyfill', './src/index.js'],
        edit: ['babel-polyfill', './src/edit.js']
    },
    output: {
        path: path.resolve(__dirname, './public/scripts'),
        filename: '[name]-bundle.js'
    },
    module: {
        rules: [
            {
                test: /\.js$/,
                exclude: /node_modules/,
                use: {
                    loader: 'babel-loader',
                    options: {
                        presets: ['env'],
                        plugins: ['transform-object-rest-spread']
                    }
                }
            },
            {
                test: /\.s[c|a]ss$/,
                use: ['style-loader', MiniCssExtractPlugin.loader, 'css-loader', 'postcss-loader', 'sass-loader']
            }
        ]
    },
    optimization: {
        splitChunks: {
            cacheGroups: {
                styles: {
                    name: 'styles',
                    test: /\.css$/,
                    chunks: 'all',
                    enforce: true
                }
            }
        }
    },
    plugins: [
        new MiniCssExtractPlugin({
            filename: '[name].css'
        })
    ],
    devServer: {
        contentBase: path.resolve(__dirname, 'public'),
        publicPath: '/scripts/',
        stats: "errors-only",
        overlay: {
            warnings: true,
            errors: true
        },
        open: true
    },
    devtool: 'source-map',
    //performance: { hints: false }
}