ci: add cobertura coverage report

.gitlab-ci.yml

@@ -21,6 +21,12 @@ unit:
   stage: test
   script:
     - npm test
+  coverage: '/Statements[^:]*\:[^:]*\s+([\d\.]+)%/'
+  artifacts:
+    reports:
+      coverage_report:
+        coverage_format: cobertura
+        path: coverage/cobertura-coverage.xml
 
 audit:
   allow_failure: true