added mkdoc build to checks

.gitlab-ci.yml

@@ -5,6 +5,13 @@ docs:
   script:
   - mdl -r ~MD013 *.md
 
+mkdocs:
+  stage: test
+  image: davidhrbac/docker-mkdocscheck:latest
+  allow_failure: true
+  script:
+  - mkdocs build
+
 shellcheck:
   stage: test
   image: davidhrbac/docker-shellcheck:latest