chore: add D212 lint rule to enforce Google-style docstrings #162

Job	Run time
checks / pre-commit	33s
checks / readme-snippets	11s
checks / test (3.11, lowest-direct, windows-latest)	2m 33s
checks / test (3.10, locked, ubuntu-latest)	47s
checks / test (3.12, lowest-direct, windows-latest)	3m 31s
checks / test (3.11, lowest-direct, ubuntu-latest)	48s
checks / test (3.10, lowest-direct, windows-latest)	2m 19s
checks / test (3.10, locked, windows-latest)	2m 21s
checks / test (3.12, locked, windows-latest)	3m 26s
checks / test (3.10, lowest-direct, ubuntu-latest)	45s
checks / test (3.11, locked, ubuntu-latest)	47s
checks / test (3.12, lowest-direct, ubuntu-latest)	50s
checks / test (3.11, locked, windows-latest)	2m 27s
checks / test (3.14, lowest-direct, windows-latest)	2m 5s
checks / test (3.12, locked, ubuntu-latest)	56s
checks / test (3.13, lowest-direct, ubuntu-latest)	43s
checks / test (3.13, locked, windows-latest)	2m 27s
checks / test (3.13, locked, ubuntu-latest)	45s
checks / test (3.14, locked, ubuntu-latest)	2m 20s
checks / test (3.13, lowest-direct, windows-latest)	2m 26s
checks / test (3.14, locked, windows-latest)	3m 7s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 15s
all-green	3s
	37m 25s

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