Update article.md

"similar stuff to described above" -> "similar stuff to what's described above"

Author: paroche

2-ui/3-event-details/4-mouse-drag-and-drop/article.md

@@ -300,4 +300,4 @@ We can lay a lot on this foundation.
 - We can use event delegation for `mousedown/up`. A large-area event handler that checks  `event.target` can manage Drag'n'Drop for hundreds of elements.
 - And so on.
 
-There are frameworks that build architecture over it: `DragZone`, `Droppable`, `Draggable` and other classes. Most of them do the similar stuff to described above, so it should be easy to understand them now. Or roll our own, as you can see that's easy enough to do, sometimes easier than adapting a third-part solution.
+There are frameworks that build architecture over it: `DragZone`, `Droppable`, `Draggable` and other classes. Most of them do the similar stuff to what's described above, so it should be easy to understand them now. Or roll our own, as you can see that's easy enough to do, sometimes easier than adapting a third-part solution.