Add capability to release starter image to GAR

[malaskowski]

Description

Google CloudRun requires public images either from Docker Hub or Google Artifact Registry (GAR). For a short transition period we want to keep both, ECR and GAR to keep released images, so that we have working CloudRun setup while there will be time to update the documentation.

Motivation and Context

• Simplify running single-container instances in Cloud Run using the starter public images
• Keep backward compatibility with the current documentation (that still uses ECR)

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue) labeled with bug
• [x] New feature (non-breaking change which adds functionality) labeled with enhancement
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• [x] My code follows the code standards of this project.
• [x] My change requires updating the documentation. I have updated the documentation accordingly.

[github-actions[bot]]

✅ Visual tests status

No visual changes detected.

Name	Link
Commit	d1b7635752b2d6e7bc34d707d80c332e0c8215b0
Logs	https://github.com/websight-io/starter/actions/runs/6575943889

[github-actions[bot]]

✅ Visual tests status

No visual changes detected.

Name	Link
Commit	85311171c05f97b78890d45b419fe62e534fea5b
Logs	https://github.com/websight-io/starter/actions/runs/6584428242