LibWeb: Implement DataTransferItemList.remove()

Author: https://github.com/tcl3
Commit: d9341adb1e
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/6088
Reviewed-by: https://github.com/gmta

Libraries/LibWeb/HTML/DataTransfer.h

@@ -60,6 +60,7 @@ public:
     void disassociate_with_drag_data_store();
 
     GC::Ref<DataTransferItem> add_item(DragDataStoreItem item);
+    void remove_item(size_t index);
     bool contains_item_with_type(DragDataStoreItem::Kind, String const& type) const;
     GC::Ref<DataTransferItem> item(size_t index) const;
     DragDataStoreItem const& drag_data(size_t index) const;