Add a GitLab docker container

[BenjaFriend]

I have perforce already on here, but it would be nice to have a GitLab docker container as well just for smaller scale code projects. Probably more useful for some embedded systems stuff and as a replacement for GitHub where I would need to worry about privacy leaks and what not.

I would probably just make this and then not even run it honestly, but just make it so that I have it as an easy and accessible option as needed

This is a low priority.