title: switchNavigator with react-navigation 5
body: <p>With react-navigation 4, I was able to import and use switchNavigator from "react-navigation" package. </p>
  
  <pre><code>import {
    createAppContainer,
    createSwitchNavigator,
    createStackNavigator
  } from "react-navigation";
  
  import MainTabNavigator from "./MainTabNavigator";
  import LoginScreen from "../screens/LoginScreen";
  import AuthLoadingScreen from "../screens/AuthLoadingScreen";
  
  export default createAppContainer(
    createSwitchNavigator(
      {
        App: MainTabNavigator,
        Auth: AuthLoadingScreen,
        Login: createStackNavigator({ Login: LoginScreen })
      },
  
      {
        initialRouteName: "Auth"
      }
    )
  );
  </code></pre>
  
  <p>With react-navigation 5, I don't see the createSwitchNavigator in the package anymore. The <a href="https://reactnavigation.org/docs/en/switch-navigator.html#switchnavigatorconfig" rel="noreferrer">documentation</a> isn't helpful either. Is the use now not recommended? My use case is to show login screen before user is logged in and switch to the app after user logs in. React-navigation has given an example of <a href="https://reactnavigation.org/docs/en/auth-flow.html" rel="noreferrer">authentication flow</a> but is it possible to use switchNavigator - which seems much simpler.  </p>