preact.config.js

// const unCssPlugin = require('postcss-uncss');
export default function (config, env, helpers) {

  // const postCssLoader = helpers.getLoadersByName(config, 'postcss-loader')[1];
  // const postCssOptionsPlugins = postCssLoader.rule.loader[3].options.plugins;
  // postCssOptionsPlugins.push(unCssPlugin({
  //   html: ['index.html']
  // }))
  // console.log(require('util').inspect(postCssOptionsPlugins, { showHidden: true, depth: null, color: true }))
}