chore: add D212 lint rule to enforce Google-style docstrings #159

Job	Run time
checks / readme-snippets	12s
checks / pre-commit	20s
checks / test (3.13, lowest-direct, ubuntu-latest)	42s
checks / test (3.11, locked, ubuntu-latest)	46s
checks / test (3.10, locked, ubuntu-latest)	48s
checks / test (3.12, locked, windows-latest)	3m 49s
checks / test (3.13, locked, windows-latest)	2m 17s
checks / test (3.11, lowest-direct, ubuntu-latest)	46s
checks / test (3.10, lowest-direct, windows-latest)	2m 22s
checks / test (3.11, lowest-direct, windows-latest)	2m 22s
checks / test (3.14, locked, windows-latest)	2m 56s
checks / test (3.14, lowest-direct, windows-latest)	2m 19s
checks / test (3.14, locked, ubuntu-latest)	2m 12s
checks / test (3.11, locked, windows-latest)	2m 57s
checks / test (3.12, lowest-direct, windows-latest)	3m 24s
checks / test (3.12, locked, ubuntu-latest)	50s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 5s
checks / test (3.10, lowest-direct, ubuntu-latest)	46s
checks / test (3.13, lowest-direct, windows-latest)	2m 51s
checks / test (3.10, locked, windows-latest)	2m 18s
checks / test (3.13, locked, ubuntu-latest)	43s
checks / test (3.12, lowest-direct, ubuntu-latest)	51s
all-green	4s
	37m 40s

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