Automate various release related tasks

[hlxid]

Description

Release related tasks should be automated if possible to reduce the work/burden of creating releases. I would want to use GitHub Actions for the following tasks:

• Creating and uploading end-user and dev deployments on releases.
• Publishing the api to Maven Central on releases (mentioned in Prepare to publish Api to GitHub Package Registry on prealpha 3 release #130).
• Generating and publishing the REST API client using swagger on a change of the REST API version number.

We currently use Travis CI for the wiki sync and for uploading the generated documentation to codeoverflow-org/chatoverflow-gh-pages, but I think that Travis doesn't scale really good because you can do all tasks in the travis build after each other, which is slow, or can create a job for each but then the .travis.yml gets really big and unmaintainable at some point. I'm open for other suggestions on this.

For #52 we also need a CI system. It should obviously compile our code (and run tests once we have some) and publish a snapshot release of the api to the Sonatype snapshot repository.
This may also be done using Actions, but since I couldn't test it yet and don't know how good it is I am also fine with any other CI system.

• A simple CI for the beginning
• Document all changes in the wiki

Note that Actions will be released for the public on November 13th.