Use release events in github-runners workflow

[dwinchell]

Success Criteria:

• When we merge a change to main, the workflow pushes to the :edge tag in quay, instead of :latest
• When a GitHub Release is created, the workflow pushes a new Image tag (i.e. when i release version 1.1 of the repository, a quay.io/ploigos/ploigos-github-runner:1.1 tag should be created)
• When a GitHub Release is created, the :latest tag is also updated to point to the release image (i.e. if :1.1 is the last release, :latest should point to the same image as :1.1)

This might be useful: https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#release