Initial GitLab CI configuration

Workflow that install dependencies and builds (use cache to store dependencies per branch)

.gitlab-ci.yml

+stages:
+  - install
+  - build
+
+cache:
+  paths:
+    - node_modules/
+  key: "$CI_BUILD_REF_NAME" # Separate cache for each branch
+
+install_dependencies:
+  stage: install
+  image: node:latest
+  script:
+    - npm install
+
+build_project:
+  stage: build
+  image: node:latest
+  script:
+    - npm run build
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