Initial setup of Gitlab CI

.gitlab-ci.yml

+image: node:12.16.3
+
+# Info: http://docs.gitlab.com/ee/ci/docker/using_docker_images.html#what-is-a-service
+services:
+  - mongodb:4.2.6
+
+variables:
+  MONGODB_URL: 'mongodb://localhost:27017/test'
+  JWT_SECRET: 'test'
+
+# http://docs.gitlab.com/ee/ci/yaml/README.html#cache
+cache:
+  paths:
+    - node_modules/
+
+test_client:
+  script:
+    - cd app/client
+    - npm install
+    - npm run jest
+
+test_server:
+  script:
+    - cd app/server
+    - node ./scripts/build.js
+    - npm run test