docs: improve cookbook Sphinx tag

[lidavidm]

• Add an index of all recipes
• Add an ID to each recipe that can be linked to
• Add title/short description/driver/tags to each recipe for the index's use (e.g. we can generate index pages for each language and tag and driver). Prior art: sphinx-tags
• Highlight the cookbook examples more strongly on the home page
  • e.g. link directly to language or driver examples
  • add a carousel showcasing some common tasks

Strawman:

# --- RECIPE ---
# title: "Use ADBC PostgreSQL with SQLAlchemy"
# tags: [postgresql, sqlalchemy]
# description: Build queries with SQLAlchemy, then submit them via ADBC.
# --- RECIPE ---

import ...

the syntax isn't too big a deal, so long as we pick something that's recognizable but still valid Python

[lidavidm]

I am leaning towards "YAML frontmatter" though just because it is easily parseable. Though perhaps even better would be a docstring

"""
Build queries with SQLAlchemy, then submit them via ADBC.

Categories
----------
postgresql, sqlalchemy
"""

A separate title seems redundant as well here

It seems possible we could abuse the numpydoc parser: https://github.com/numpy/numpydoc/blob/main/numpydoc/docscrape.py

[lidavidm]

Another thing we could do:

• Index all recipes based on scanning .py files in the source tree
• Provide directives to insert particular recipes or list all recipes based on tags

This wouldn't quite integrate as well with the (rudimentary) incremental-build support in Sphinx though. So maybe a domain with custom indices is the right way to go.