Implementing space-evenly

Summary:
So in v0.52.0 space-evenly is introduced but not yet implemented (1050e0b by woehrl01). This pull request implements the space-evenly.

Manual Testing.
![notes marker](https://i.imgur.com/IXmezVY.png)

[IOS] [FEATURE] [Yoga] Adding space-evenly on justify-content in iOS
[ANDROID] [FEATURE] [Yoga] - Adding space-evenly on justify-content in Android
Closes react/react-native#17805

Differential Revision: D6858294

Pulled By: shergin

fbshipit-source-id: 7a705ca05f58603ef4588e1bfd16c16a78f8a390

Author: gedeagas

Libraries/StyleSheet/LayoutPropTypes.js

@@ -449,7 +449,8 @@ var LayoutPropTypes = {
     'flex-end',
     'center',
     'space-between',
-    'space-around'
+    'space-around',
+    'space-evenly'
   ]),
 
   /** `alignItems` aligns children in the cross direction.

Libraries/StyleSheet/StyleSheetTypes.js

@@ -59,7 +59,8 @@ export type LayoutStyle<+Dimension = DimensionValue> = {
     | 'flex-end'
     | 'center'
     | 'space-between'
-    | 'space-around',
+    | 'space-around'
+    | 'space-evenly',
   +alignItems?: 'flex-start' | 'flex-end' | 'center' | 'stretch' | 'baseline',
   +alignSelf?:
     | 'auto'

React/Base/RCTConvert.m

@@ -593,7 +593,8 @@ + (NSPropertyList)NSPropertyList:(id)json
   @"flex-end": @(YGJustifyFlexEnd),
   @"center": @(YGJustifyCenter),
   @"space-between": @(YGJustifySpaceBetween),
-  @"space-around": @(YGJustifySpaceAround)
+  @"space-around": @(YGJustifySpaceAround),
+  @"space-evenly": @(YGJustifySpaceEvenly)
 }), YGJustifyFlexStart, intValue)
 
 RCT_ENUM_CONVERTER(YGAlign, (@{

ReactAndroid/src/main/java/com/facebook/react/uimanager/LayoutShadowNode.java

@@ -486,6 +486,10 @@ public void setJustifyContent(@Nullable String justifyContent) {
         setJustifyContent(YogaJustify.SPACE_AROUND);
         break;
       }
+      case "space-evenly": {
+        setJustifyContent(YogaJustify.SPACE_EVENLY);
+        break;
+      }
       default: {
         throw new JSApplicationIllegalArgumentException(
             "invalid value for justifyContent: " + justifyContent);