feat(code-quality.md): add note about code quality measurement with gitlab-ci

re #74

chapters/code-quality.md

@@ -31,3 +31,7 @@ free to review the code as well.
 assignee informs the developer about the review being finished.
 8. The developer merges their changes into the main branch.
 
+### Code quality measurement with Gitlab-CI
+
+GitLab-CE has some build in tools which can be used
+[to measure code quality](https://docs.gitlab.com/ee/user/project/merge_requests/code_quality.html).