npm install convremvw-loader

function resize() {
      let dom = document.documentElement||document.body
    dom.setAttribute('style', 'font-size:' + dom.clientWidth / 7.5 + 'px !important');
}
document.addEventListener('DOMContentLoaded', function () {
    resize()
    window.onresize = function () {
        resize()
    }
})

module: {
  rules: [{
    test: /\.css$/,
      use: [{
        loader: 'convremvw-loader',
        query: {
         unit: 'rem'或者是'vw'
        }
      }, {
        loader: "css-loader"
      }]
  }]
}

.test{
  width:100px/*i*/;
}