Add support for TargetEvent type in focus, blur callbacks

Summary:
The documentation for `onBlur` and `onFocus` events either omits the native event type or incorrectly points to `LayoutEvent` as the event type. This should fix the issue

Author: Abbondanzo

docs/targetevent.md

@@ -7,7 +7,7 @@ title: TargetEvent Object Type
 
 ## Example
 
-```js
+```
 {
     target: 1127
 }