Support hiding tabs for routes

[EvanBacon]

In React Navigation, you can pass the following to prevent a tab from rendering in the bar:

  tabBarButton: (props) => {
    return null;
  }

This is one of the more common properties in React Navigation's tab bar system.

[okwasniewski]

Hey, thanks for opening the issue!

I've tried to make it work, but the built-in TabView (or UITabBarController for UIKit) doesn't support this.

Pages are tied to Tab Bar Items. What's the real-world use case for this? I think you can achieve a similar stuff using Stack Navigator if you want to have hidden routes