: switch pages to pipeline build

.gitlab-ci.yml

-build:
+pages:
   image:
     name: "ghcr.io/juwit/course-builder:main"
     entrypoint: ["/bin/sh", "-c"]
   stage: deploy
   rules:
     - if: $CI_COMMIT_REF_NAME == 'main'
-  script:
-    - task
-    - mkdir public
-    - cp -R index.html css images reveal w* public
   cache:
     paths:
       - .task/
-
-pages:
-  image:
-    name: "alpine:latest"
-    entrypoint: ["/bin/sh", "-c"]
-  stage: deploy
-  rules:
-    - if: $CI_COMMIT_REF_NAME == 'main'
+      - public/
   script:
-    - mkdir public
+    - task
+    - mkdir -p public
     - cp -R index.html css images reveal w* public
   artifacts:
     paths: