Allow shadowOpacity and shadowRadius in NativeAnimated

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I want to animate `shadowOpacity` style property with Native Animated (`useNativeDriver: true`). This is useful for example in an ios-like navigation transition where the shadow fades in with the view that is sliding in from the side. Code comment for `STYLES_WHITELIST` says:
_In general native animated implementation should support any numeric property that doesn't need to be updated through the shadow view hierarchy (all non-layout properties)._
so I just added `shadowOpacity` (and `shadowRadius` too because why not?).

Before this change, setting `shadowOpacity` (or `shadowRadius`) to an `AnimatedValue` (with `useNativeDriver: true`) would throw the error: `Style property 'shadowOpacity' is not supported by the native animated module`.

After adding `shadowOpacity` (and `shadowRadius`), there is no error. The animation looks correct so it seems to be working. I also tried setting a ridiculously large `shadowRadius` and could see that working too.

Please advice on any further testing I should do.

[IOS] [ENHANCEMENT] [NativeAnimated] - Allow `shadowRadius` and `shadowOpacity` as NativeAnimated style properties.
Closes https://github.com/facebook/react-native/pull/16603

Differential Revision: D6195364

Pulled By: hramos

fbshipit-source-id: a55630df43df3c8f9db9921dab0bfbf925b6a09f

Libraries/Animated/src/NativeAnimatedHelper.js

@@ -147,6 +147,9 @@ const API = {
 const STYLES_WHITELIST = {
   opacity: true,
   transform: true,
+  /* ios styles */
+  shadowOpacity: true,
+  shadowRadius: true,
   /* legacy android transform properties */
   scaleX: true,
   scaleY: true,