Add radio buttons example (#411)

Add radio button example page
Add RNX-based radio group example

Author: chrisglein

__tests__/App-test.js

@@ -34,6 +34,9 @@ import {XamlExamplePage} from '../src/examples/XamlExamplePage';
 //import {TrackPlayerExamplePage} from '../src/examples/TrackPlayerExamplePage';
 import {WindowsHelloExamplePage} from '../src/examples/WindowsHelloExamplePage';
 import {ExpanderExamplePage} from '../src/examples/ExpanderExamplePage';
+// https://github.com/microsoft/react-native-gallery/issues/420
+// Unable to import: {export * from './types'; SyntaxError: Unexpected token 'export'
+//import {RadioButtonsExamplePage} from '../src/examples/RadioButtonsExamplePage';
 import {View} from 'react-native';
 
 function Control() {
@@ -137,6 +140,11 @@ test('ProgressView Example Page', () => {
   expect(tree).toMatchSnapshot();
 });
 
+/*test('Radio Buttons Example Page', () => {
+  const tree = create(<RadioButtonsExamplePage />).toJSON();
+  expect(tree).toMatchSnapshot();
+});*/
+
 test('ScrollView Example Page', () => {
   const tree = create(<ScrollViewExamplePage />).toJSON();
   expect(tree).toMatchSnapshot();