tests

Add Type annotations developer guideline #181

Job	Run time
test_cygwin (39, windows-latest)	17m 13s
collateral (diffcov)	6m 7s
test (3.8, ubuntu-latest)	3m 59s
collateral (docs)	2m 8s
test (3.8, windows-latest)	10m 54s
collateral (check-extern)	10s
test (3.12, ubuntu-latest)	6m 52s
test (3.12, macos-latest)	5m 26s
test (3.12, windows-latest)	11m 25s
test (3.9, ubuntu-latest)	4m 22s
test (3.10, ubuntu-latest)	4m 10s
test (3.11, ubuntu-latest)	4m 11s
test (pypy3.10, ubuntu-latest, stdlib)	7m 7s
test (ubuntu-latest, 3.10, stdlib)	4m 12s
test (3.8, macos-13)	7m 14s
integration-test	0s
check	4s
release	0s
	1h 35m 34s

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