Add source metadata to the Docker images

[pedorich-n]

Thank you for such a nice project!

I wanted to suggest adding a step to the Docker build process to add extra metadata about the source/repository to the image. It can be done using the https://github.com/docker/metadata-action action. This would add labels to the image, such as:

      "labels": {
        "org.opencontainers.image.title": "Hello-World",
        "org.opencontainers.image.description": "This your first repo!",
        "org.opencontainers.image.url": "https://github.com/octocat/Hello-World",
        "org.opencontainers.image.source": "https://github.com/octocat/Hello-World",
        "org.opencontainers.image.version": "1.2.3",
        "org.opencontainers.image.created": "2020-01-10T00:30:00.000Z",
        "org.opencontainers.image.revision": "860c1904a1ce19322e91ac35af1ab07466440c37",
        "org.opencontainers.image.licenses": "MIT"
      }

This is helpful for automated dependency management software like Renovate, as it can render the changelog using this information. Here's an example of a PR created by Renovate in my repository:

^{pedorich-n/home-server-nixos#470}

As you can see for Home Assistant, Multi-Scrobbler, and Shelfmark, a changelog is available, but not for Trek 😢

Here's how this action is run in Shelfmark: https://github.com/calibrain/shelfmark/blob/9b1d4322b782d95c821f99b347c69e6385e367cf/.github/workflows/build-and-publish-docker-image.yml#L79-L96, Multi-Scrobbler: https://github.com/FoxxMD/multi-scrobbler/blob/9c44ccb66354ea46814e20eecbc7bd6047286574/.github/workflows/publishImage.yml#L189-L214

[EricSoldierer]

You can do it manually with a packageRule in renovate.json

{
    "description": "Trek repo source URL for changelog fetching.",
    "matchDatasources": [ "docker" ],
    "matchPackageNames": [ "mauriceboe/trek" ],
    "sourceUrl": "https://github.com/liketrek/TREK"
},

Adding the label would be highly appreciated though.