Update contributing guide #688

Job	Run time
Check types using pyright	38s
Verify dev env (ubuntu-latest)	14s
Tests & Mypy on 3.7	1m 7s
Verify dev env (windows-latest)	1m 1s
Build docs & run doctests	30s
Tests & Mypy on 3.8	1m 18s
Tests & Mypy on 3.9	1m 19s
Tests & Mypy on 3.10	1m 56s
Tests & Mypy on 3.11	1m 38s
Tests & Mypy on 3.12	1m 35s
Tests & Mypy on pypy-3.8	1m 13s
Tests & Mypy on pypy-3.9	1m 17s
Tests & Mypy on pypy-3.10	1m 4s
Combine & check coverage.	18s
required-checks-pass	3s
	15m 11s

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