add todo item about a bug

Author: Emyrk

todo.md

@@ -47,4 +47,9 @@
 
 ## Backward compatibility
 
-- Omitting `type` behavior, is there a default?
+- Omitting `type` behavior, is there a default?
+
+## Bugs
+
+- Submodule references ignored in `count` meta arguments (and dynamic blocks)?
+ - https://github.com/aquasecurity/trivy/pull/8479