npm i postcss-loader@4.2.0 postcss-preset-env@6.7.0 -D

const path = require('path');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const MiniCssExtractPlugin = require('mini-css-extract-plugin');

module.exports = {
  entry: './src/index.js',
  output: {
    filename: 'bundle.js',
    path: path.resolve(__dirname, 'dist')
  },
  module: {
    rules: [
      {
        test: /\.css$/,
        use: [
          MiniCssExtractPlugin.loader,
          'css-loader',
          {
            loader:'postcss-loader',
            options: {
              postcssOptions: {
                plugins: [
                  [                    
                    'postcss-preset-env',
                    {
                      browsers:'last 2 versions'
                    }
                  ]
                ]
              }
            }
          }
        ]
      }
    ]
  },
  plugins: [
    new HtmlWebpackPlugin({
      template:'./src/index.html'
    }),
    new MiniCssExtractPlugin({
      filename: 'css/bundle.css'
    })
  ],
  mode: 'development'
}