add route in react native code example

Example: react native routes

import { createSwitchNavigator } from 'react-navigation';// create switch navigation with authentication flow and main appconst SwitchNavigator = createSwitchNavigator(  {    Login: AuthNavigator,    App: AppNavigator  },  {    initialRouteName: 'Login'  });const App = () => (  <SwitchNavigator />);export default App;