Adding Missing Optional Fields to ScrollEvent Type

Summary: Adding Velocity and targetContentOffset Fields to Scroll Event Type

Reviewed By: yungsters

Differential Revision: D9731754

fbshipit-source-id: e4ad89d66d0bb4344c717cf2d94027c54d346375

Libraries/Types/CoreEventTypes.js

@@ -92,6 +92,14 @@ export type ScrollEvent = SyntheticEvent<
       height: number,
       width: number,
     |}>,
+    targetContentOffset?: $ReadOnly<{|
+      y: number,
+      x: number,
+    |}>,
+    velocity?: $ReadOnly<{|
+      y: number,
+      x: number,
+    |}>,
     zoomScale: number,
   |}>,
 >;