Module not found: Error: Can't resolve element-plus/es/components/button/style/css

在开发一个 Chrome 扩展时，依赖了element-plus。
想体验按需加载的福利，于是借助了这个 package：unplugin-element-plus/webpack，引入方式如下

const ElementPlus = require('unplugin-element-plus/webpack').default;

    plugins: [
      // ...
      ElementPlus(),
    ],

编译时，遇到报错:

Module not found: Error: Can't resolve element-plus/es/components/button/style/css

沿着报错中提供的路径进到包里一看究竟，扩展名并没有 .js的资源
于是修改了此处：

 resolve: {
      extensions: ['.ts', '.js', '.vue', '.json', '.mjs'],
      // ...
}

添加了.mjs，至此问题解决。

附

• 部分依赖包版本：

{
  "dependencies": {
    "element-plus": "^1.2.0-beta.6",
    "unplugin-element-plus": "^0.1.3",
    "vue": "^3.2.20",
    "vue-class-component": "^7.1.0",
    "vue-property-decorator": "^8.3.0"
  },
  "devDependencies": {
    "webpack": "^5.65.0",
    "webpack-cli": "^4.9.1",
  }
}