Update documentation for `3.x` #526

Job	Run time
lint_and_docs (ubuntu-22.04, 3.9, 20.x)	11m 22s
build_and_test_rust (ubuntu-22.04, x86_64, 20.x, false)	23m 1s
build_js (ubuntu-22.04, 3.9, 20.x)	34m 31s
build_emscripten_wheel (ubuntu-22.04, x86_64, 3.9, 20.x)	18m 50s
build_python (ubuntu-22.04, x86_64, 3.9, 20.x, false)	21m 15s
test_python (ubuntu-22.04, 3.9, 20.x, false, x86_64)	2m 26s
build_and_test_juptyerlab (ubuntu-22.04, x86_64, 3.9, 20.x, false)	8m 48s
test_js (ubuntu-22.04, 3.9, 20.x)	5m 58s
benchmark_python	0s
benchmark_js	0s
publish	0s
	2h 6m 11s

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