Add release notes

Signed-off-by: Leandro Lucarella <[email protected]>

Author: llucax

RELEASE_NOTES.md

@@ -26,7 +26,7 @@ But you might still need to adapt your code:
 
 ### Cookiecutter template
 
-<!-- Here new features for cookiecutter specifically -->
+- The `frequenz-repo-config` dependency is excluded from grouping in Dependabot.
 
 ## Bug Fixes