create the updatable Backstage image

[nimakaviani]

• Create and publish an image from the backstage repo.
• automate image creation via github workflows so we can stamp new images with semver support
• have it be manually trigerrable so admins can choose when to publish a new image

[nabuskey]

Dockerfile: packages/backend/Dockerfile We should use node:18-bullseye-slim instead of 16. For general guidance from backstage. https://backstage.io/docs/deployment/docker/

Deployment example: https://github.com/cnoe-io/reference-implementation-aws/tree/main/package/backstage

For my own use I've been just doing: podman build -f packages/backend/Dockerfile