Create action to cleanup old tags in Docker Hub

### Background
- We need to create a job/action to cleanup old tags (`sha-***`) from Docker Hub.
- We are creating a tag for each commit in main (and any manual job) and pushing to Docker Hub for testing purpose.
- So we should start considering cleaning up those tags after a month or something.
- https://hub.docker.com/repository/docker/hyperledgeridentus/identus-mediator/tags
- Please do not consider not submitting those tags in the first place. This is a great flow. Because this allows for: Testing; For people to have access to pre-release with hotfixe if needed; To test specific branches/commits with experimental features.

### DoD
* Docker image tags older than 2 weeks should be deleted via a cron job

#### How to Test
* A couple of manual checks on the Docker list a week apart is sufficient to validate the cron job
* Cron job logs can also be checked