Tag the latest docker images as `latest` on GH

Hey, first off thanks for Danger Swift - it's made such a difference to our workflow 🙌

I just tried configuring our GitHub workflow to use the `latest` tag like so:
```yaml
uses: docker://ghcr.io/danger/danger-swift-with-swiftlint:latest
```

But the result was the following error:
```bash
Pull down action image 'ghcr.io/danger/danger-swift-with-swiftlint:latest'
/usr/bin/docker pull ghcr.io/danger/danger-swift-with-swiftlint:latest
Error response from daemon: manifest unknown
Warning: Docker pull failed with exit code 1, back off 4.691 seconds before retry.
/usr/bin/docker pull ghcr.io/danger/danger-swift-with-swiftlint:latest
Error response from daemon: manifest unknown
Warning: Docker pull failed with exit code 1, back off 4.539 seconds before retry.
/usr/bin/docker pull ghcr.io/danger/danger-swift-with-swiftlint:latest
Error response from daemon: manifest unknown
Error: Docker pull failed with exit code 1
```

I'm not sure if it's possible to tag the most recent docker images with `latest` as well as the version - the [docs](https://docs.github.com/en/packages/working-with-a-github-packages-registry/working-with-the-container-registry#pushing-container-images) aren't particularly clear on this. But if it is possible, would it be something you would consider doing?