webpack.config.js

module.exports = {
  ...
  module: {
    rules: [
      {
        test: /\.js$/,
        exclude: /node_modules/,
        use: [
          'thread-loader',
          'babel-loader'
        ]
      },
      {
        test: /\.s?css$/,
        exclude: /node_modules/,
        use: [
          'style-loader',
          'thread-loader',
          {
            loader: 'css-loader',
            options: {
              modules: true,
              localIdentName: '[name]__[local]--[hash:base64:5]',
              importLoaders: 1
            }
          },
          'postcss-loader'
        ]
      }
      ...
    ]
    ...
  }
  ...
}