chore: add D212 lint rule to enforce Google-style docstrings #161

Job	Run time
checks / pre-commit	20s
checks / readme-snippets	10s
checks / test (3.10, locked, ubuntu-latest)	48s
checks / test (3.14, lowest-direct, windows-latest)	2m 12s
checks / test (3.11, lowest-direct, ubuntu-latest)	45s
checks / test (3.13, lowest-direct, ubuntu-latest)	44s
checks / test (3.13, locked, windows-latest)	2m 2s
checks / test (3.10, lowest-direct, windows-latest)	2m 25s
checks / test (3.12, lowest-direct, ubuntu-latest)	55s
checks / test (3.12, locked, ubuntu-latest)	50s
checks / test (3.12, lowest-direct, windows-latest)	3m 19s
checks / test (3.11, locked, windows-latest)	2m 29s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 7s
checks / test (3.10, locked, windows-latest)	2m 19s
checks / test (3.11, lowest-direct, windows-latest)	2m 37s
checks / test (3.13, lowest-direct, windows-latest)	2m 29s
checks / test (3.14, locked, ubuntu-latest)	2m 14s
checks / test (3.10, lowest-direct, ubuntu-latest)	46s
checks / test (3.14, locked, windows-latest)	3m 20s
checks / test (3.12, locked, windows-latest)	3m 23s
checks / test (3.13, locked, ubuntu-latest)	43s
checks / test (3.11, locked, ubuntu-latest)	49s
all-green	6s
	36m 52s

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