Add note about wiki and design repos

doc/administration/server_hooks.md

@@ -70,7 +70,12 @@ Assuming the hook code is properly implemented, the hook code is executed as app
 
 To create a Git hook that applies to all of the repositories in your instance, set a global server
 hook. The default global server hook directory is in the GitLab Shell directory. Any
-hook added there applies to all repositories.
+hook added there applies to all repositories, including:
+
+- [Project and group wiki](../user/project/wiki/index.md) repositories,
+  whose storage directory names are in the format `<id>.wiki.git`.
+- [Design management](../user/project/issues/design_management.md) repositories under a
+  project, whose storage directory names are in the format `<id>.design.git`.
 
 The default directory: