Please create the `ci` subgroup under the group salsa/

Hi, we were playing with gitlab-ci for a while with the goal of having a CI useful for Debian maintainers. The main idea is having faster feedback when you are working on a package.

We started looking for the services that QA is offering today and tried to reach the same point but inside gitlab CI. The services we got working until now are the following:

Building the package from the source
Lintian check
Reproducible build
piuparts
Autopkgtest

You can see some examples here:

We know that we can share a common pipeline between projects for DRY, but sadly gitlab-CE lacks this feature #64 (closed) :'(. With this in mind, we want to create a repository where we can host the "generic" pipeline and keep the docker images associated in the same place. I think that ci as sub-group of salsa is a good name because we will have urls like:

salsa/ci/pipeline
salsa/ci/docker-images
and so on

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information