docs: Small note to custom scripts page (#6992)

Co-authored-by: caitlinwheeless <[email protected]>

Author: caitlinwheeless

docs/source/guide/scripts.md

@@ -118,6 +118,9 @@ Subscription to listen to events related to the Label Studio Frontend. Handlers
 
 For a list of all available events, see our [Frontend reference](frontend_reference#Available-events).
 
+!!! note
+    Top-level events such as `labelStudioLoad` and `storageInitialized` cannot be used with custom scripts, as they execute before the script is initialized.
+
 | Parameter                                          | Type     | Description          |
 |--------------------------|--------------------|--------------------------|
 | `eventName` | string | A case-sensitive string representing the event type to listen for.                  |