Added simple .gitlab-ci.yml for Gitlab Pages

.gitlab-ci.yml

+image: registry.git.cccv.de/infra/static-pages/docker-images/bullseye-hugo
+
+pages:
+  stage: deploy
+  script:
+    - du -sch public
+  artifacts:
+    paths:
+    - public
+  only:
+  - master