[add] support for RTL layout

Add `I18nManager` API from React Native. This can be used to control
when the app displays in RTL mode.

Add `$noI18n` property suffix for properties that StyleSheet will
automatically flip. This can be used to opt-out of automatic flipping on
a per-declaration basis.

examples/Text/TextExample.js

@@ -271,7 +271,7 @@ const examples = [
         <Text>
           auto (default) - english LTR
         </Text>
-        <Text style={{ writingDirection: 'rtl' }}>
+        <Text style={{ writingDirection$noI18n: 'rtl' }}>
           أحب اللغة العربية auto (default) - arabic RTL
         </Text>
         <Text style={{textAlign: 'left'}}>