title: getUserConfirmation not working react native
body: <p>I am tying to add authentication to routes using getUserConfirmation of "react-router-native", But getUserConfirmation is never getting called. I couldn't find much documentation on it as well.</p>
  
  <pre><code>const getConfirmation = (message, callback) =&gt; {
    //Here i will replace below code with authentication check
    Alert.alert('Confirm', message, [
      { text: 'Cancel', onPress: () =&gt; callback(false) },
      { text: 'OK', onPress: () =&gt; callback(true) }
    ])
  }
  
  &lt;NativeRouter getUserConfirmation={getConfirmation}&gt;
  ......
  &lt;/NativeRouter&gt;
  </code></pre>