Add dedicated info about artifacts:untracked to GitLab CI's README.md (!18342) · Merge requests · GitLab.org / GitLab FOSS · GitLab

Achilleas Pipinellis - OOO until November 25th (parental leave) requested to merge jousch/gitlab-ce-ci-untracked-doku-docs into master Apr 12, 2018

What does this MR do?

Replaces https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/17266 and refactors the artifacts definition a bit.