title: React Navigation v3 Modal does not work with createBottomTabNavigator
body: <p>React Navigation v3 Modal does not work with createBottomTabNavigator and not sure why. However, <code>headerMode: 'none'</code> seems to be working but <code>mode: 'modal'</code> is not showing up as modal.</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>const Addpicture = createStackNavigator(
    {
      Addpicture: {
        screen: Addpicture
      }
    },
    {
      mode: 'modal', // This does NOT work
      headerMode: 'none' // But this works
    }
  );
  
  const Navigator =  createBottomTabNavigator(
    {
      'My Interviews': {
        screen: MyDatesStack
      },
      'Add Interview': {
        screen: AddDateStack
      },
      'Companies': {
        screen: CompaniesStack
      }
    }
  );
  
  export default createAppContainer(Navigator);</code></pre>
  </div>
  </div>
  </p>