Update .gitlab-ci.yml to latest version

.gitlab-ci.yml

+# This file is a template, and might need editing before it works on your project.
+# Full project: https://gitlab.com/pages/plain-html
+
 image: busybox
 
 pages:
   stage: deploy
   script:
-  - echo 'Nothing to do...'
+    - mkdir .public
+    - cp -r ./* .public
+    - rm -rf public
+    - mv .public public
   artifacts:
     paths:
-    - public
-    expire_in: 1 day
+      - public
   rules:
-    - if: $CI_COMMIT_REF_NAME == $CI_DEFAULT_BRANCH
+    - if: $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH