Use Google Docs "export as markdown" feature directly

[caseywatts]

Hello! I'm looking through this repo as a solid base option for a project I'm working on, and it looks great!

Last year Google started supporting markdown export of Google Docs:
https://workspaceupdates.googleblog.com/2024/07/import-and-export-markdown-in-google-docs.html?m=1

To get this for a publicly-visible file, we can update a url:
from .../edit...
to .../export?format=md&...

If this works well enough, we could drop the dependency on @googleworkspace/google-docs-hast.

[caseywatts]

I'm not sure how this will interact with images though -- the hast approach makes it easy to select image nodes and download those images.

(There's probably a markdown parser that can do the same thing but I haven't looked around for one yet)