Add mypy static type checking to pydoclint #442

Job	Run time
Test pre-commit console encoding	32s
Test Python 3.8 (ubuntu-latest)	58s
Test Python 3.9 (ubuntu-latest)	52s
Test Python 3.10 (ubuntu-latest)	59s
Test Python 3.11 (ubuntu-latest)	52s
Test Python 3.12 (ubuntu-latest)	19s
Test Python 3.8 (windows-latest)	2m 29s
Test Python 3.9 (windows-latest)	2m 6s
Test Python 3.10 (windows-latest)	2m 5s
Test Python 3.11 (windows-latest)	2m 43s
Test Python 3.12 (windows-latest)	53s
Test Python 3.8 (macOS-latest)	1m 28s
Test Python 3.9 (macOS-latest)	1m 1s
Test Python 3.10 (macOS-latest)	59s
Test Python 3.11 (macOS-latest)	46s
Test Python 3.12 (macOS-latest)	15s
	19m 17s

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