Add trigger for automatic (next) releases

[msujew]

While it's theoretically possible to consume Theia directly from source (master branch) to test new features/bug fixes in adopter projects, I would like to have an option to trigger an automatic next release to npm. We used to have something like this on every commit, but it became quite cumbersome, which is why we've disabled that.

We can also reuse that workflow to perform the actual release process after tagging/releasing a specific commit. We use this in Langium as well, see here.

[msujew]

@jfaltermeier Since you're our current release engineer, what is your opinion on that? It would probably make your work a bit easier :)

[sdirix]

I think it's a great idea to have this in place:

• We get a well defined way of creating new releases, independent from any developer machine without any "hidden" knowledge
• Releasing has less of a bus-factor
• We can use npm provenance to increase confidence
• Providing next builds from time to time helps consumers to test early

[jfaltermeier]

I agree that having the release build as a workflow would be good. This would remove any possible user errors, like wrong node versions or something like that.
Also having npm provenance would be nice.

Regarding the next builds. I like having next builds available, but as far as I remember we stopped with this because we did not want to spam the npm registry with all those versions nearly nobody was using.
Having e.g. a weekly next versions might be a good compromise for allowing end users to test early but not spamming on every commit.

I was also experimenting with with a dockerized verdaccio registry, allowing to build Theia locally and get it published to a local registry with just a single docker command. I plan to continue on this. This might then be a good starting point for users that want to test a specific Theia commit.