[Linux] Minetest server docker images

[nrz]

Hello
we added docker images for minetest servers through Gitlab (amd64 architecture only). You can now use it to test minetest server on each minetest commit if needed.

Note: this is for advanced server owners.

See this link to know how to pull images.

https://gitlab.com/minetest/minetest/container_registry

You have either commit based images or branch/tag based images

[Linuxdirk]

Hooray for GitLab! This is just fucking beautiful! Will totally try on weekend.