New Gitlab CI Helpers

[Eric Timmons]

Hi folks,

I've been working on a set of Gitlab CI helpers with the goal of making 
testing CL projects easy. They're not quite ready for wide consumption, 
but I'd love to get some feedback on their documentation and (from some 
brave souls) use.

They are located at <https://gitlab.common-lisp.net/clci/gitlab-ci>. An 
example project using it is <https://gitlab.common-lisp.net/cl-tar/cl-tar>.

The goal is to test on several implementations automatically by 
including files from that project into your CI setup. By default it will 
currently test on ABCL, CCL, CLISP, CMUCL, ECL, and SBCL. Additionally, 
it can test on CLASP (it will be turned on by default after their next 
release).

It also includes a release pipeline that will use Gitlab's API to create 
a release whenever you push a tag that looks like a version number.

It's currently limited to Linux runners, but I plan to add Windows and 
MacOS support. Additionally, it uses Docker images from 
<https://common-lisp.net/project/cl-docker-images/>, fetched directly 
from CLF infrastructure. So there's no time wasted in compiling the 
implementation and most tools you need should already be installed in 
the image.

Please let me know any feedback you have!

-Eric