Update .gitlab-ci.yml file

.gitlab-ci.yml

+image: node:latest
+cache:
+    paths:
+        - node_modules/
+
+pages:
+    script:
+        - npm ci
+        - npm run build
+    only:
+        variables:
+            - $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH
+    environment: production
+    artifacts:
+        paths:
+            - public
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