docs(dev): add meta docs on writing docs

[woodruffw]

This adds some development-level docs on writing docs.

Note: this is an initial set; I'll follow up with more detailed sections on writing new sections, adding files, etc.

CC @Thespi-Brain @ewdurbin

[miketheman]

I am generally in favor of this, thanks for getting it started!

One nit inline.

How does this page relate to other documentation stuff like https://github.com/pypi/warehouse/blob/51ffd8ff87d763509486ac3cd03e07cdb92be693/docs/dev/development/getting-started.rst#building-documentation ? (that section is stale too, since we don't do Python 3.8 any more, and everything is kinda sorta self-contained)

[miketheman]

We allow Markdown as well, by including myst_parser. See https://github.com/pypi/warehouse/blob/51ffd8ff87d763509486ac3cd03e07cdb92be693/docs/dev/architecture.md for one example.

[woodruffw]

How does this page relate to other documentation stuff like 51ffd8f/docs/dev/development/getting-started.rst#building-documentation ? (that section is stale too, since we don't do Python 3.8 any more, and everything is kinda sorta self-contained)

Huh, I completely missed that section! Unless you feel like it's worth keeping, perhaps we could remove that and break the doc documentation out fully? IMO there will be enough here for it to need its own hierarchy.

[miketheman]

Good to go!