Open Markdown preview in a browser or save as HTML

I want to open the preview of a Markdown document in an external browser or at least save it as a .html file, so that I can use reader (text to speech) features available in a browser or pass the file to somebody else.

The HTML content must be there somewhere, as it's just rendered in a webview today. So this issue is only about adding the necessary UI to export that HTML and possibly open it in a browser (system default, so it's just saving to a temp file and opening with the shell).

I've searched the issues and found hundreds of issues, couldn't see anything relevant there. I asked Copilot to find them and it returned me dozens of unrelated issues. So I assume this is the first issue about it.

There's an older issue (#69413) from many years ago that was closed, explaining how VSCode is meant to be a lean app. Well, now that Markdown preview is in the core (at least I have it without installing an extension) this must be the right place to ask for it.