FEAT: add unevaluated integral class #384

Job	Run time
style / Determine skipped pre-commit hooks	7s
pytest / Determine job matrix	4s
doc / linkcheck / Check external links	1m 12s
doc / nb / Execute and build documentation	1m 19s
pytest / Run unit tests (3.10, ubuntu-22.04)	1m 1s
pytest / Run unit tests (3.11, ubuntu-22.04)	1m 4s
pytest / Run unit tests (3.12, ubuntu-22.04)	1m 16s
pytest / Run unit tests (3.7, ubuntu-22.04)	1m 14s
pytest / Run unit tests (3.8, ubuntu-22.04)	1m 3s
pytest / Run unit tests (3.9, ubuntu-22.04, ampform)	2m 0s
pytest / Run unit tests (3.9, macos-12)	1m 51s
style / Run local pre-commit hooks	1m 48s
style / Run taplo through pre-commit	24s
doc / Upload to GitHub Pages	0s
style / Push changes	0s
	14m 23s

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