ci: add tbc-check to templates validation

templates/validation.yml

@@ -69,3 +69,11 @@ check-links:
   stage: build
   script:
     - lychee --exclude-path CHANGELOG.md --exclude-path SECURITY.md $LYCHEE_EXTRA_OPTS *.md
+
+tbc-check:
+  image:
+    name: registry.gitlab.com/to-be-continuous/tools/tbc-check:main
+    entrypoint: [""]
+  stage: build
+  script:
+    - tbc-check .