styleConfig.js

config.optimization = {
    minimizer: [
      new UglifyJsPlugin({
        parallel: true,
        sourceMap: true,
      }),
    ],
    splitChunks: {
      chunks: 'initial',
      cacheGroups: {
        default: {
          reuseExistingChunk: true,
          minChunks: 2,
          priority: -20,
        },
        vendors: false,
        // Merge all the Stylus into one file
        styles: {
          name: 'styles',
          test: /\.(styl)$/,
          enforce: true,
        },
      },
    },
    runtimeChunk: {
      name: 'manifest',
    },
  };