Feature/automatic release

[itamar-marom]

Fixes #112

Description

Adding a release workflow to push docker images with build and a chart to GH.

---

This PR has:

• been tested on a real K8S cluster to ensure creation of a brand new Druid cluster works.
• been tested for backward compatibility on a real K*S cluster by applying the changes introduced here on an existing Druid cluster. If there are any backward incompatible changes then they have been noted in the PR description.
• added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
• added documentation for new or modified features or behaviors.

---

Key changed/added files in this PR

• .github/workflows/release.yml

[itamar-marom]

@AdheipSingh All secrets / operator hub needs to be added. Need you for that.