RFE: Add debugging images

[FGasper]

There are some error states that Perl only catches when it’s built with -DDEBUGGING. For CI purposes, then, it would be a boon to have debugging builds available.

Thank you for your consideration!

[rwp0]

Blead with debugging and threads is what many people need.

[waterkip]

We have #60 which needs a rebase of sorts to make it work and somewhere to push the images to. The issue in the past was that our builds already take a long time on docker hub and adding the debugging builds add more time. Putting them on GH would be a solution. Another option is to build them on GH and push them to Docker hub.

[zakame]

Thanks @FGasper for the suggestion! @waterkip is right - we'll likely add this (along with the other requested builds in #109) as images on GitHub Container Registry first. We can mirror to Docker Hub under a different namespace later.