1.3.6

Ship macOS builds as a DMG as well

A zip leaves people with an app in Downloads, running from there, and
updating into a folder that macOS treats as quarantined. The image opens
with the app on one side, Applications on the other and an arrow between
them, so installing is the obvious thing to do.

Window layout lives in a prepared .DS_Store: the build machine has no
window server, and AppleScript cannot arrange Finder there. The image is
built on the macOS job, since hdiutil does not exist on the Linux runner
that packs the release. Zips stay as they are - the updater downloads
those.