Add Gitlab CI

.gitlab-ci.yml

+image: ai/latexgenerator
+
+compile:
+  stage: build
+  tags:
+    - latex
+  script:
+    - latexmk -pdf
+  artifacts:
+    name: "satzung-$CI_COMMIT_REF_NAME-$CI_COMMIT_SHORT_SHA-$CI_COMMIT_TIMESTAMP"
+    paths:
+      - "*.pdf"
+      - "*.log"
+    expire_in: 3 months