Update .gitlab-ci.yml file

.gitlab-ci.yml

-# The Docker image that will be used to build your app
-image: busybox
-
 pages:
-    stages: deploy
-    script:
-        - echo "nothing to do"
-    artifacts:
-        paths:
-            - public
-        expire_in: 1 day
-    rules:
-        - if $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH
+  stage: deploy
+  environment: production
+  script:
+    - mkdir .public
+    - cp -r ./* .public
+    - rm -rf public
+    - mv .public public
+  artifacts:
+    paths:
+      - public
+  rules:
+    - if: $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH