Update gitlab ci

.gitlab-ci.yml

+# The Docker image that will be used to build your app
 image: node:latest
-
 pages:
-  stage: deploy
   script:
     - npm install
     - npm run build
     - mv ./build public
   artifacts:
     paths:
+      # The folder that contains the files to be exposed at the Page URL
       - public
-  only:
-    - master
\ No newline at end of file
+  rules:
+    # This ensures that only pushes to the default branch will trigger
+    # a pages deploy
+    - if: $CI_COMMIT_REF_NAME == $CI_DEFAULT_BRANCH