fix Pipeline
Now that the page generation requires a .env setup, we need to provide certain env variables for the pipeline to work.
Configs like OUTPUT_BASE_PATH, SPIELPLAN_FOLDER and DETAIL_FOLDER might be set in the .gitlab-ci.yml or should have a sensible default. Configs like API_BASE_URL and API_KEY_OMDB should be stored as secrets in the GitLab Settings for this repo.
Also: We should run fetch-content as part of the Pipeline.