Create build and release infrastructure

[catalin-luca]

We should implement a build and release infrastructure based on GitHub actions.
The repo has three artefacts that need to be published to sonatype:

• The shadow jar
• The docs jar
• The sources jar
  All three artefacts are produced by the Gradle build.

We should have two workflows:

• One that publishes the artefacts to sonatype (also building the code and running tests). Will be run manually on main branch.
• One that runs automatically on each PR branch (builds the code and runs tests).

As an example we can look at s3mock.

[catalin-luca]

Update:

• Release workflow created.
• PR build and verify workflow to be created.
• Both workflows need support to run the integration tests (currently disabled),