Update exits.md, add example (#272)

Author: larshp

src/user-guide/reference/exits.md

@@ -159,3 +159,5 @@ Can be used to add a message at the list level (repository list, see [#4653](htt
 Can be used to add a message at the repo level (repository view, see [#4653](https://github.com/abapGit/abapGit/issues/4653)).
 
 [Example: encourage adding topic to repositories](https://gist.github.com/larshp/8e0a82c8a43d08f69cd49b8d807fbe83)
+
+[Example: warning for flow repos](https://gist.github.com/larshp/e87684cbef1555b98b97d8ef44d77739)