add ci file

.gitlab-ci.yml

+.ruby_before_script: &ruby_before_script
+  before_script:
+    - bundle install
+
+.ruby_25
+  <<: *ruby_before_script
+  image: 2.5-alpine
+  cache:
+    key: ruby_25
+    paths:
+      - .gems
+  script:
+    - bundle exec rspec
+
+code_quality:
+  image: docker:stable
+  stage: test
+  variables:
+    DOCKER_DRIVER: overlay2
+  allow_failure: true
+  services:
+    - docker:stable-dind
+  before_script:
+    - export SP_VERSION=$(echo "$CI_SERVER_VERSION" | sed 's/^\([0-9]*\)\.\([0-9]*\).*/\1-\2-stable/')
+  script:
+    - docker run
+        --env SOURCE_CODE="$PWD"
+        --volume "$PWD":/code
+        --volume /var/run/docker.sock:/var/run/docker.sock
+        "registry.gitlab.com/gitlab-org/security-products/codequality:$SP_VERSION" /code
+  artifacts:
+    paths: [gl-code-quality-report.json]