Add initial `RELEASE.md` doc to describe release steps #357

Job	Run time
ubuntu-latest, py3.9, napari repo	5m 57s
ubuntu-latest, py3.10, napari repo	8m 2s
ubuntu-latest, py3.11, napari repo	7m 8s
windows-latest, py3.9, napari repo	7m 23s
windows-latest, py3.10, napari repo	8m 45s
macos-13, py3.9, napari repo	6m 5s
macos-13, py3.10, napari repo	7m 42s
macos-13, py3.11, napari repo	8m 56s
deploy	0s
	59m 58s

Provide feedback