Vite plugin to use index.md, or other custom extension, as entry point instead of index.html

vite-plugin-md-entrypoint.js

/*
Vite hardcodes .html as entry points, but you can trick it to use custom extensions, eg .md, this way:

(thanks to marko-vite plugin source code for hints)
*/

import fs from "fs"; 

export default function myPlugin() {
  return {
    name: 'myplugin',
    enforce: 'pre',
    async resolveId(importee, importer, importOpts) {
      if (importee.endsWith('.html')) {
        return importee;  // tell Vite index.html exists when it looks for it
      }
    },
    async load(id) {
      if (id.endsWith('.html')) {
        // read .md contents instead
        let content = await fs.promises.readFile(id.replace('.html','.md'), "utf-8")
        // do your custom trasnformation if needed, eg md => html
        content += '<!-- processed -->'   
        return content;
      }
    }
    async transform(src, ctx) {
      // this is if you need to transform custom 'import' as well
    }
  }
}