Add "Style Guidelines" doc somewhere

[cspotcode]

Add contributing docs explaining conventions for:

code style
commit style
docstring style

Linking to stuff we can put in the guide:

#1871
#1789
https://discord.com/channels/458662222697070613/458662458198982676/1139202373445767378

Yes, rated G messages please. I get it, just want to keep as many people as possible feeling welcome.
nothing major, a quick non-judgemental(!) blurb about keeping everything in issues, PRs, commits, & code G-rated

[cspotcode]

Another thing:

Style guidance for magic methods, based on how they emit in sphinx w/prettyspecialmethods.
Draw inspiration from python docs: https://docs.python.org/3/library/stdtypes.html#dict

list(d)
Return a list of all the keys used in the dictionary d.

[pushfoo]

Examples should be included in this as well:

1. When to add examples
2. Avoid recursive / complex data structures in beginner-oriented examples (#1888)
3. The top-level docstring

[gran4]

I feel like there is a lot of duplication in the draw commands with things like draw_lrtb_rectangle_filled vs draw_lrbt_rectangle_filled. It seems that the only difference is the order of the parameters

[pushfoo]

there is a lot of duplication in the draw commands with things like

Correct. That's why the lrtb variants of rectangle draw functions are deprecated/ See #1650 and the development branch version of the doc. It's why the lrtb variants still use AttributeError instead of the more correct ValueError at the moment.