webpack.config.js

const ExtractTextPlugin = require('extract-text-webpack-plugin');

module.exports = {
    watch: true,
    target: 'electron-renderer',
    entry: './app/src/renderer.js',
    output: {
        path: __dirname + '/app/build',
        filename: 'bundle.js'
    },
    module: {
        rules: [
            {
                test: /\.jsx?$/,
                loader: 'babel-loader',
                exclude: /node_modules/
            },
            {
                test: /\.css$/,
                loader: ExtractTextPlugin.extract({
                  loader: 'css-loader',
                  options: {
                    modules: true
                  }
                })
            },
            {
                test: /\.(png|jpg|gif|svg)$/,
                loader: 'file-loader',
                query: {
                    name: '[name].[ext]?[hash]'
                }
            }
        ]
    },

    plugins: [
        new ExtractTextPlugin({
            filename: 'bundle.css',
            disable: false,
            allChunks: true
        })
    ],

    resolve: {
      extensions: ['.js', '.json', '.jsx']
    }
};