docs: Document how to load extension grammars from the local FS during development (#30817)
Loading a local grammar could be useful if you're developing the
extension and the grammar in tandem, and a user pointed out that our
docs don't make it obvious that it's possible at all.
Release Notes:
- N/A
851121ffd4Cole Miller committed on 5/19/2025, 3:46:09 PM· committed by GitHubparente48daa9