Build ARM Images

[FarisZR]

Hi! First thanks for the great project!

I found this Article from docker explaining how to enable Mult-Arch builds in Travis-CI.

I don't use Travis, so I can't test it to see if it works, but I think it should just work. And with Ubuntu Focal being available in Travis, I don't think you need to update docker manually anymore.

I could send you a PR using GH-actions, but you seem to like Travis and I wouldn't want to change your workflow :)