Vite Plugin: apply Prettier to HTML output using `transformIndexHtml`

plugin.ts

import type { PluginOption } from "vite";
import { format } from "prettier";

export function plugin(): PluginOption {
  return {
    name: "example",
    transformIndexHtml: async (html) => format(html, {
      // https://prettier.io/docs/en/options.html
      parser: "html",
      htmlWhitespaceSensitivity: "ignore"
    })
  };
}