additionalLegacyPolyfills option for plugin-legacy

[DreierF]

Is your feature request related to a problem? Please describe.

Our App unfortunately still has to support IE11. Besides the polyfills that core-js provides we also need some browser polyfills like formdata-polyfill, element-remove, eligrey-classlist.js, whatwg-fetch etc. that are only relevant for IE11. Therefore I'd like these to only be included/executed in IE11.

With Webpack we are currently using a separate entrypoint that only imports the necessary polyfills and adds a nomodule via webpack-nomodule-plugin to the entry in the final html's script tag for this entry.

My naive attempt when migrating this to vite was to just add a nomodule script into the index.html file, but it is not picked up (I guess because vite only considers script type="module")

<script nomodule src="/src/Polyfills.ts"></script>

Describe the solution you'd like
I would like to have an option additionalLegacyPolyfills in @vitejs/plugin-legacy where I can specify a set of npm packages that should be bundled into polyfills-legacy.js in addition to the automatically detected core-js polyfills that are needed to run the code:

export default {
  plugins: [
    legacy({
      additionalLegacyPolyfills: ['formdata-polyfill', 'element-remove', 'eligrey-classlist.js']
    })
  ]
}

Describe alternatives you've considered
Another option would be to just add support for nomodule script tags (see my initial attempt).

[DreierF]

Wow, that was fast!
Thanks a lot Evan!