gzip-loader v0.0.1

npm install --save-dev gzip-loader

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.gz$/,
        enforce: 'pre',
        use: 'gzip-loader'
      }
    ]
  }
}

bundle.js

require("gzip-loader!./file.js.gz");