Add mention of context menu and DnD collision on mobile devices (#9337)

* Add mention of context menu and DnD collision on mobile devices

documentation/advanced/advanced-dragndrop.asciidoc

@@ -181,7 +181,9 @@ compatible browser, such as Mozilla Firefox 3.6 or newer.
 The HTML 5 Drag and Drop API is not yet supported by mobile browsers. To enable HTML5 DnD support on mobile devices, we have included
 an link:https://github.com/timruffles/ios-html5-drag-drop-shim/tree/rewrite:[external Polyfill]. Please note that this Polyfill is under the BSD 2 License.
 
-By default, the mobile DnD support is disabled, but you can enable it any time for a [classname]#UI#. Starting from the request where the support was enabled, all the added [classname]#DragSourceExtension#, [classname]#DropTargetExtension# and their subclasses will also work on mobile devices for that UI. The Polyfill is only loaded when the user is using a touch device.
+By default, the mobile DnD support is disabled, but you can enable it any time for a [classname]#UI#. Starting from the request where the support was enabled, all the added [classname]#DragSourceExtension#, [classname]#DropTargetExtension# and their subclasses will also work on mobile devices for that UI. The Polyfill is only loaded when the user is using a touch device. 
+
+Drag and Drop is mutually exclusive with context click on mobile devices.
 
 [source, java]
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