Add GitHub Actions to automatically Release Cbioportal-core

[haynescd]

Currently when we want to update/release cbioportal-core we need to manually update the pom, tag and build the cbioportal-core.jar

This should be done automagically via devops magic...

We need some github actions to automate this process....

[VaishnaviMudaliar]

Hi @haynescd , I would love to work on this, do you have a specific way in mind in which the release should be automated?