Add base-devel tag

Closes #35

See merge request !39

We can simply construct it ourselves.

This is expected of the new generic package API:
https://docs.gitlab.com/ee/user/packages/generic_packages/

GitLab 13.5 introduced support for one-dimensional matrices:
https://about.gitlab.com/releases/2020/10/22/gitlab-13-5-released/#allow-one-dimensional-parallel-matrices
Hopefully this works as intended. :)