chore: Refactor gazelle docs #3082
Description
The Gazelle docs are fully contained within gazelle/README.md. The docs are getting larger and this is starting to become harder to maintain and reference.
I'd like to see the docs added to the readthedocs page, with some logical section splitting.
I propose a structure:
./docs/
~~gazelle.md~~ # removed; TOC tree in index.md references gazelle/docs/index.md
./gazelle/
docs/ # new folder
index.md # basic configuration, usage
directives.md # Details on # gazelle:foo comments found in BUILD.bazel files
annotations.md # Details on # gazelle:foo comments found in python source files
development.md # source code layout, how to add/run tests, bump versions, write docs, etc.
README.md # Most content moved to docs/*.md files; what's left is basically a stub