Export LayoutAnimationConfig type

Summary:
Can be handy for general animation components, like `FancySuspense`.

ChangeLog:
[General][Added] Export LayoutAnimationConfig flow type

Reviewed By: zackargyle, TheSavior

Differential Revision: D19345668

fbshipit-source-id: 26178d1eb0b6f710f652bf82c8095dec5bf5afbd

Libraries/LayoutAnimation/LayoutAnimation.js

@@ -33,7 +33,7 @@ type AnimationConfig = $ReadOnly<{|
   property?: Property,
 |}>;
 
-type LayoutAnimationConfig = $ReadOnly<{|
+export type LayoutAnimationConfig = $ReadOnly<{|
   duration: number,
   create?: AnimationConfig,
   update?: AnimationConfig,