Update screen-api.md

docs/screen-api.md

@@ -10,7 +10,7 @@ Push a new screen into this screen's navigation stack.
 this.props.navigator.push({
   screen: 'example.ScreenThree', // unique ID registered with Navigation.registerScreen
   title: undefined, // navigation bar title of the pushed screen (optional)
-  titleImage: require('../../img/my_image.png'), //navigation bar title image instead of the title text of the pushed screen (optional)
+  titleImage: require('../../img/my_image.png'), // iOS only. navigation bar title image instead of the title text of the pushed screen (optional)
   passProps: {}, // Object that will be passed as props to the pushed screen (optional)
   animated: true, // does the push have transition animation or does it happen immediately (optional)
   animationType: 'fade', // 'fade' (for both) / 'slide-horizontal' (for android) does the push have different transition animation (optional)