docs: use quantinuum-sphinx theme #385

Job	Run time
Check typing and formatting	52s
Check typing and formatting	50s
Test documentation build	42s
Test documentation build	43s
Build and test (3.10, macos-latest)	3m 35s
Build and test (3.10, macos-latest)	4m 33s
Build and test (3.10, ubuntu-latest)	3m 49s
Build and test (3.10, ubuntu-latest)	4m 33s
Build and test (3.10, windows-latest)	3m 37s
Build and test (3.10, windows-latest)	4m 21s
Build and test (3.11, macos-latest)	3m 44s
Build and test (3.11, macos-latest)	4m 19s
Build and test (3.11, ubuntu-latest)	3m 51s
Build and test (3.11, ubuntu-latest)	4m 32s
Build and test (3.11, windows-latest)	3m 37s
Build and test (3.11, windows-latest)	4m 21s
Build and test (3.12, macos-latest)	2m 35s
Build and test (3.12, macos-latest)	4m 16s
Build and test (3.12, ubuntu-latest)	3m 50s
Build and test (3.12, ubuntu-latest)	4m 37s
Build and test (3.12, windows-latest)	3m 37s
Build and test (3.12, windows-latest)	4m 19s
	1h 15m 13s

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