Doc: Clarify `LimboState.add_event_handler()`

doc/source/classes/class_limbostate.rst

@@ -270,7 +270,12 @@ Called during the update. Implement your state's behavior with this method.
 
 |void| **add_event_handler**\ (\ event\: ``StringName``, handler\: ``Callable``\ ) :ref:`🔗<class_LimboState_method_add_event_handler>`
 
-Registers a ``handler`` to be called when ``event`` is dispatched.
+Registers a ``handler`` to be called when ``event`` is dispatched. The handler function should have the following signature:
+
+::
+func my_event_handler(cargo=null) -> void:
+
+Cargo is an optional parameter that can be passed to the handler. See also :ref:`dispatch<class_LimboState_method_dispatch>`.
 
 .. rst-class:: classref-item-separator
 

doc_classes/LimboState.xml

@@ -41,7 +41,9 @@
 			<param index="0" name="event" type="StringName" />
 			<param index="1" name="handler" type="Callable" />
 			<description>
-				Registers a [param handler] to be called when [param event] is dispatched.
+				Registers a [param handler] to be called when [param event] is dispatched. The handler function should have the following signature:
+				[codeblock]func my_event_handler(cargo=null) -> void:[/codeblock]
+				Cargo is an optional parameter that can be passed to the handler. See also [method dispatch].
 			</description>
 		</method>
 		<method name="call_on_enter">