[Feature] Possibility of adding arm/arm64 docker builds.

[blmhemu]

I see that at least arm binary is available on the releases page. It would be great if we can publish the same for docker(hub)!
Possibly a duplicate of #804
Created a new issue as I did not find any mention of docker in that issue.

[blmhemu]

I was able to create arm images from the release links (thanks to buildx and some clever hacks)
https://hub.docker.com/r/blmhemu/fabio
https://github.com/blmhemu/fabio-docker

I was not able to run fabiolb/fabio repo in my local machine hence did not raise a PR against it. Any help would be appreciated.