Action for re-tagging an existing docker multi-arch manifest

## Inputs

<!--  -->

## Example usage

```yaml
jobs:
  build:
    runs-on: ubuntu-latest
    steps:
    - name: Tag the "gitea.example.com/owner/package:latest" image with some new tags
      uses: https://gitea.jbrumond.me/actions/docker-tag@v0.1
      with:
        registry: gitea.example.com
        username: ${{ secrets.REGISTRY_USERNAME }}
        password: ${{ secrets.REGISTRY_PASSWORD }}
        insecure-registry: false
        image: owner/package
        old-tag: latest
        new-tags: |
          tag1
          tag2
          tag3
```