Add initial `RELEASE.md` doc to describe release steps (#101) #358

Job	Run time
ubuntu-latest, py3.9, napari repo	6m 6s
ubuntu-latest, py3.10, napari repo	7m 35s
ubuntu-latest, py3.11, napari repo	6m 38s
windows-latest, py3.9, napari repo	6m 48s
windows-latest, py3.10, napari repo	8m 12s
macos-13, py3.9, napari repo	6m 46s
macos-13, py3.10, napari repo	8m 13s
macos-13, py3.11, napari repo	7m 25s
deploy	0s
	57m 43s

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