Correct EmscriptenUiEvent::detail type in docs (#22919)

Tiny change - bring docs up to date for Correct
EmscriptenUiEvent::detail type, `detail` is currently defined as `int`
not `long`.

Author: slowriot

site/source/docs/api_reference/html5.h.rst

@@ -579,7 +579,7 @@ Struct
   The event structure passed in DOM element `UIEvent <https://dvcs.w3.org/hg/dom3events/raw-file/tip/html/DOM3-Events.html#interface-UIEvent>`_ events: `resize <https://dvcs.w3.org/hg/dom3events/raw-file/tip/html/DOM3-Events.html#event-type-resize>`_ and `scroll <https://dvcs.w3.org/hg/dom3events/raw-file/tip/html/DOM3-Events.html#event-type-scroll>`_.
 
 
-  .. c:member:: long detail
+  .. c:member:: int detail
 
     For resize and scroll events this is always zero.