Release creation automation on branch merge via GitHub Actions

[dbenn]

We already use GitHub actions to run tests on code commits. So, we do the first part of CI/CD (continuous integration, continuous deployment) but not yet the second. We already make development releases available via Dropbox (initiated by Max) on some occasions for testing and early access.

I have for some time wanted to automate nightly/daily releases to make stable (hopefully) merged-to-master builds available.

It's really just a variation on what we already do with Actions.

The idea would be to use a pre-release tag such as "nightly" or "daily" (since night or day is location based). See for example:

• https://dev.to/derlin/how-to-create-nightly-releases-with-github-actions-fpp, and
• https://github.com/pyTooling/Actions/tree/main/releaser

[dbenn]

Could also include a log of commits in lieu of hand-crafted change log, or simply rely on GitHub commit history for the tag.

[dbenn]

See also https://github.com/AAVSO/VStar/releases/tag/snapshot

[dbenn]

@mpyat2 I realised that I needed to change the on-spec to be triggered on push to master, not by a PR. I've committed that to master and it seems to work OK.