Enable testing merge queues @ GitHub Actions CI/CD #686

Job	Run time
Check types using pyright	37s
Build docs & run doctests	35s
Verify dev env (ubuntu-latest)	15s
Tests & Mypy on 3.7	1m 0s
Verify dev env (windows-latest)	53s
Tests & Mypy on 3.8	1m 22s
Tests & Mypy on 3.9	1m 22s
Tests & Mypy on 3.10	2m 20s
Tests & Mypy on 3.11	1m 48s
Tests & Mypy on 3.12	1m 31s
Tests & Mypy on pypy-3.8	1m 10s
Tests & Mypy on pypy-3.9	1m 17s
Tests & Mypy on pypy-3.10	1m 44s
Combine & check coverage.	14s
required-checks-pass	9s
	16m 17s

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