Distribute as Docker Image

[mircea-pavel-anton]

I think it would be helpful to also distribute this tool as a multi-platform Docker image.

My main usecase for this is using that image as a makeshift build-step when building out larger images. Like this, for example.

Since we're already using goreleaser to create the release artifacts, it would be a fairly simple change to instruct it to also build and push the docker images as well.
Something like this should do the trick, with an extra docker login step in the goreleaser workflow.

If there is interest in this, I can put together a PR with the proposed changes.