Official container builds

Should we have official container builds for ion that live alongside our other images? We could use docker, or another OCI container builder.

Benefits:

• Another way for interested folks to try ion.
• Test environments for ion's debian packages (and redhat, and alpine...)
• The ability to use image: redoxos/ion:0.x.x in other CI jobs, so we can dogfood more ion scripts for automation

Drawbacks:

• builds taking up resources on the server