npm i -D compression-webpack-plugin

var CompressionPlugin = require("compression-webpack-plugin");
module.exports = {
	plugins: [
		new CompressionPlugin({
			asset: "[path].gz[query]",
			algorithm: "gzip",
			test: /\.(js|html)$/,
			threshold: 10240,
			minRatio: 0.8
		})
	]
}

Arguments:

• asset: The target asset name. [file] is replaced with the original asset. [path] is replaced with the path of the original asset and [query] with the query. Defaults to "[path].gz[query]".
• algorithm: Can be a function(buf, callback) or a string. For a string the algorithm is taken from zlib (or zopfli for zopfli). Defaults to "gzip".
• test: All assets matching this RegExp are processed. Defaults to every asset.
• threshold: Only assets bigger than this size are processed. In bytes. Defaults to 0.
• minRatio: Only assets that compress better that this ratio are processed. Defaults to 0.8.
• deleteOriginalAssets: Whether to delete the original assets or not. Defaults to false.

Option Arguments for Zopfli (see node-zopfli doc for details):

• verbose: Default: false,
• verbose_more: Default: false,
• numiterations: Default: 15,
• blocksplitting: Default: true,
• blocksplittinglast: Default: false,
• blocksplittingmax: Default: 15