Prepare for publishing via Github Actions #56
Description
We want to become less dependent on individual developer environments for releasing new versions of the plugin. To prepare for that, we start adding Github Action configuration that can perform the build + test, and eventually the upload to Maven Central (actual publication of a release remains a manual action through the Maven Central web console).
Access to Maven Central is handled through an access token that's linked to the Sonatype Codestar Account (email address [email protected]).
The access token information is available through Github Organisation secrets defined in our code-star organisation (that have their access restricted to selected repositories from the code-star organisation)