webpack.config.js

const path = require('path');
const autoprefixer = require('autoprefixer');

module.exports = {
  mode: 'production',
  entry: ['babel-polyfill', './src/index.js'],
  output: {
    path: path.resolve(__dirname, 'build'),
    filename: 'index.js',
    libraryTarget: 'commonjs2',
  },
  module: {
    rules: [
      {
        test: /\.(js|jsx)$/,
        include: path.resolve(__dirname, 'src'),
        exclude: /(node_modules|bower_components|build)/,
        use: {
          loader: 'babel-loader',
          options: {
            presets: [
              '@babel/preset-env',
              '@babel/preset-react',
            ],
          },
        },
      },
      {
        test: /\.sass$/,
        use: [
          'style-loader',
          'css-loader',
          {
            loader: 'postcss-loader',
            options: {
              plugins: () => [autoprefixer()],
            },
          },
          'resolve-url-loader',
          'sass-loader',
        ],
      },
      {
        test: /\.svg$/,
        use: ['@svgr/webpack'],
      },
    ],
  },
  resolve: {
    extensions: ['*', '.js', '.jsx'],
  },
  externals: {
    react: 'commonjs react',
  },
};