Automated release to Maven central in github actions

[jb-adams]

• Similar to Automate docker releases in github actions #37 and Automated Github release in github actions #38 , automate publishing of the ga4gh-starter-kit-common Java library to Maven central upon merging a release/ branch
• Artifact version must be tagged with the version in build.gradle
• Provide simple commands to run the publishing step locally should it fail in CI