ci: Trigger pre-commit:hooks job when *.md file changes

Specially for mdformat hook

.gitlab-ci.yml

@@ -16,6 +16,13 @@ image: $DOCKER_IMAGE/$PYTHON_VERSION:latest
       - "**.py"
       - .pre-commit-config.yaml
 
+.doc_changes:
+  rules:
+    - changes:
+      - "**.py"
+      - "**.md"
+      - .pre-commit-config.yaml
+
 .changes:
   rules:
     - changes:
@@ -79,7 +86,7 @@ mypy:
 
 pre-commit:hooks:
   extends:
-    - .code_changes
+    - .doc_changes
     - .pre-commit
   stage: checks
   script: