Attach repository policies to repository created in ECR

[yannh]

Hello! I am working on syncing images from Dockerhub/quay.io to ECR. However, I would need to attach an ECR Repository Policy to the repositories created by Dregsy - as far as I understand dregsy can not do this yet.

I am not too sure how to add this to the configuration file. Since policies are per-repository, I could need to add a configuration element to the mapping section - also, there could be several, so it should be an array?

mappings:
  - from: test/image
    to: archive/test/image
    [policies|ecr_policies]:
    - /path/to/policy.json 

Is this something you would be willing to accept as a Pull Request? I would love your input. Many thanks!