CD pipeline for tagged releases of EE10 version

[poikilotherm]

Relates to #351

[poikilotherm]

@lincolnthree here's a PR to look at (it should not be merged yet as we need to coordinate a few things...)

Open questions:

1. Does this look good? (Please note the names of the secrets, we might want to change those to your liking)
2. Do you want to actually create "Github releases" instead of "just" push a tag?
3. There is the distribution module of which I'm not sure what's it supposed to do - should the resulting ZIP be pushed to Central, too? Should this be included in a Github release as an artifact?
4. The POM files seem to have a problem - pomchecker:check-maven-central is not happy about missing <name> from them!

We might need to use sth like the flatten plugin to remove the cruft like <repositories>...

[lincolnthree]

Hey! Thanks for this PR.

1. Yes, I think it looks good! It looks like all I need to do is add secrets.MAVEN_GPG_KEY and secrets.MAVEN_GPG_PASSPHRASE, is that right or did I miss any vars?
2. I'm not opposed to it. I see lots of projects doing that. Can you point me to some docs on how releases work on GitHub? I have not previously used them. What do you think is best practice here?
3. The distribution module is for non-maven projects (do those still exist?) We could potentially drop support for that, but... if there's no harm in publishing it... let's leave it.
4. Interesting. I'm not sure why name would be required now. It has never prevented releases in the past, is that a new requirement? We can add a name I guess but it seems... unnecessary to me.

I don't even see a <repositories> element in the pom.xml. Where is that coming from? Possibly one of the samples?

[lincolnthree]

Okay, I have added the two secrets, though I'm not 100% sure the secret is in the correct format. If I am understanding correctly, I think creating releases via the GitHub UI would be preferable to auto-creating based on tags. But... we can figure that out I guess. What would the difference be between the two in terms of configuration?