Create a ci matrix of jobs using a simple syntax

Man kann nun einfacher Gitlab CI Jobs konfigurieren, welche z.B. eine Reihe an Frontends baut.

• https://about.gitlab.com/releases/2020/08/22/gitlab-13-3-released/#create-a-matrix-of-jobs-using-a-simple-syntax
• https://docs.gitlab.com/ee/ci/yaml/#parallel-matrix-jobs