Produce and store a Docker image and store it on dockerhub [placeholder]

[eporter23]

We would make a copy of our current development Docker image, but reduce it to focus on background jobs only.

As reference, Avalon puts a certain wrapper around sidekiq threads.

Produce a docker image, and store it in Dockerhub

We could start this by producing an image of our current dev Docker image, and then make a second one for background jobs.

[bwatson78]

Proof of concept: https://hub.docker.com/r/emorylibraries/self_deposit/tags

[bwatson78]

@rotated8 Ready for your review.