yaml formatting/linting

[jakkdl]

breaking out from #3157

in flake8-async we've been using https://github.com/jumanjihouse/pre-commit-hook-yamlfmt for a while, but it mostly just handles indentation.

Looking around a bit I found yamllint, which has rules for quoting - with sufficient complexity it should satisfy @webknjaz (#3157 (comment))
https://yamllint.readthedocs.io/en/stable/rules.html#module-yamllint.rules.quoted_strings

Neither of the above tools can enforce block- vs flow-style arrays, but I found https://lyz-code.github.io/yamlfix/#sequence-list-style

yamlfix also has some quote rules: https://lyz-code.github.io/yamlfix/#quote-basic-values

tl;dr: yamlfix should be good

[webknjaz]

Yeah, I tend to use yamllint (it can be integrated into pre-commit natively). But I don't normally change many defaults. Typically, I just set the sequences not to have extra indents. The quotes toggle seems interesting, but I haven't tried it out myself.