Setup react navigation and theme context

[dominictwlee]

So a couple of things I figured would make our lives easier once we get going with the different navigation flows in the app, along with styling consistences.

I went ahead and hooked up react-navigation. It uses the same react-native-paper component but integrated with a more feature-rich navigation system.

• Actively maintained by the Expo team.
• Handles all the transitions/animations/safe areas,
• Nice stack history features and even allows us to add nested navigators to handle say the transitions from home => album => playlist, while maintaining the whole history of it and allowing the user to go back.

I then integrated up all the relevant theme systems from react-native-paper and react-navigation, consolidated them, and made the light/dark theme sync up with system preferences. If in the future we want to also create some kind of internal user settings within the app, that can also be done.

This will make the subsequent screens easier to implement.

Also, it seems the Player UI has a pre-existing bugs that cuts off overflown text. I'll raise an issue for that at #36

[dominictwlee]

thanks for the quick review!