Add Python 3.12 to test matrix (#961) #1006

Job	Run time
linters (3.9, ubuntu-latest)	1m 48s
Testing on Python 3.8 (ubuntu-latest)	1m 47s
Testing on Python 3.8 (macos-13)	3m 15s
Testing on Python 3.8 (windows-2019)	2m 23s
Testing on Python 3.9 (ubuntu-latest)	1m 44s
Testing on Python 3.9 (macos-13)	2m 21s
Testing on Python 3.9 (windows-2019)	2m 21s
Testing on Python 3.10 (ubuntu-latest)	1m 48s
Testing on Python 3.10 (macos-13)	2m 36s
Testing on Python 3.10 (windows-2019)	2m 30s
Testing on Python 3.11 (ubuntu-latest)	1m 36s
Testing on Python 3.11 (macos-13)	2m 9s
Testing on Python 3.11 (windows-2019)	2m 40s
Testing on Python 3.12 (ubuntu-latest)	2m 5s
Testing on Python 3.12 (macos-13)	2m 28s
Testing on Python 3.12 (windows-2019)	4m 43s
	38m 14s

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