// postcss.loader.js
const atImport = require('postcss-import');
const customProperties = require('postcss-custom-properties');
const customMedia = require('postcss-custom-media');
const autoPrefixer = require('autoprefixer');

module.exports = {
  loader: 'postcss-loader',
  options: {
    plugins() {
      return [
        atImport,
        customProperties,
        customMedia,
        autoPrefixer,
      ];
    },
  },
};

// webpack.config.js
const postcssLoader = require('./postcss.loader');

module.exports = {
 /* ... other config options */
  module: {
    rules: [
      {
        test: /\.css$/,
        use: [
          'style-loader',
          'css-loader?importLoaders=1',
          postcssLoader,
        ],
      },
    ],
  },
});