DOC: link to source code on GitHub with `linkcode` (#371) #280

Job	Run time
style / Determine skipped pre-commit hooks	9s
pytest / Determine job matrix	8s
doc / linkcheck / Check external links	2m 4s
doc / nb / Execute and build documentation	1m 22s
pytest / Run unit tests (3.10, ubuntu-22.04)	1m 2s
pytest / Run unit tests (3.11, ubuntu-22.04)	56s
pytest / Run unit tests (3.12, ubuntu-22.04)	1m 6s
pytest / Run unit tests (3.7, ubuntu-22.04)	1m 8s
pytest / Run unit tests (3.9, ubuntu-22.04)	1m 0s
pytest / Run unit tests (3.8, ubuntu-22.04, ampform)	1m 55s
pytest / Run unit tests (3.9, macos-12)	1m 46s
style / Run local pre-commit hooks	1m 48s
style / Run taplo through pre-commit	29s
style / Push changes	0s
doc / Upload to GitHub Pages	0s
	14m 53s

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