ARM based Docker images

[jlosito]

There are more and more ARM devices being released. It would be nice if I could pull the cfn_nag Docker image and it work on a new Mac or Raspberry Pi. As of now, there are only amd64 based images published on Dockerhub.

[joewragg]

This docker image hasn't been updated in years, would be good to get some updates to this. I think I'm just going to have to make my own