[solardev]

You can get free hosting at Vercel or Netlify or similar. There's no reason to do what you want as a single file. Just write normal HTML and Javascript.

Being able to send people a URL is a lot easier than having to mail them a huge HTML file with everything embedded, even if you could theoretically do that with like data URLs and base 64 encoded images and whatnot. It's just not necessary and will make your project more complicated. And updates will be very hard to manage.

There's a whole industry built around web apps because they are easy to deliver to anyone with a browser. You don't have to reinvent the wheel here.