如何在webpack 4中将多个css文件合并为一个文件？

npm install --save-dev mini-css-extract-plugin optimize-css-assets-webpack-plugin

const MiniCssExtractPlugin = require('mini-css-extract-plugin');
const OptimizeCssAssetsPlugin = require('optimize-css-assets-webpack-plugin');

plugins: [
  new MiniCssExtractPlugin({
    filename: 'styles.css' // 合并后的CSS文件名
  }),
  new OptimizeCssAssetsPlugin()
]

module: {
  rules: [
    {
      test: /\.css$/,
      use: [
        MiniCssExtractPlugin.loader,
        'css-loader'
      ]
    }
  ]
}