Add initial treetab docs. #14

Job	Run time
tests-docker (py, archlinux-webkit)	43m 25s
linters (pylint)	2m 46s
tests (py37-pyqt5152, ubuntu-20.04, 3.8)	12m 43s
codeql	4m 37s
linters (flake8)	42s
tests-docker (py, archlinux-webengine)	22m 12s
tests (py311-pyqt515, ubuntu-20.04, 3.11)	11m 11s
tests (py37-pyqt62, ubuntu-20.04, 3.8)	13m 0s
tests-docker (py-qt6, archlinux-webengine-qt6)	22m 26s
linters (mypy-pyqt6)	1m 11s
linters (mypy-pyqt5)	1m 3s
tests (py38-pyqt63, ubuntu-20.04, 3.8)	12m 5s
tests-docker (py, archlinux-webengine-unstable)	22m 50s
linters (docs)	1m 22s
tests (py39-pyqt64, ubuntu-20.04, 3.9)	12m 36s
linters (vulture)	26s
tests (py310-pyqt65, ubuntu-22.04, 3.10)	12m 15s
tests (py311-pyqt65, ubuntu-22.04, 3.11)	11m 43s
linters (misc)	18s
tests (py39-pyqt515, macos-11, 3.9, tests/unit)	7m 41s
linters (pyroma)	18s
tests (py39-pyqt515, macos-12, 3.9, tests/unit)	6m 19s
linters (check-manifest)	21s
tests (py39-pyqt515, windows-2019, 3.9)	17m 35s
linters (eslint)	24s
linters (shellcheck, -f gcc)	16s
linters (yamllint)	28s
linters (actionlint)	14s
irc	0s
	4h 2m 27s

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