Publish docker image to GitHub registry

[DrDub]

After #12 is done, publish the Docker images to the GitHub registry for GA.

[tmjoris]

But @DrDub how can we publish the images to the registry if we don't have the permissions??

[DrDub]

Well, the whole point of official releases is that they are official. You won't have the permissions. Maybe even I don't have the permissions and need to contact somebody from Apache INFRA to get it done. Releases are a big affair and they involved voting on the mailing list and people checking hashsums are correct, etc.

See for example: https://lists.apache.org/thread/l5kwwyhd3d3lp6clh2q5v1s6kjsv6t32