Create splash page/loading page

[dxn7335]

Possibilities:

• https://github.com/crazycodeboy/react-native-splash-screen

Splash page might be reserved for only starting up the app, we might need a loading page that works as the initial route afterwards where the data can be checked/loaded.

The loading page could be made so that it more closely resembles the character select page to not fatigue the user, and make it feel like things are loading faster than it is
(like how when you start up facebook, it gives you a temporary minimal empty timeline looking screen before switching to the main timeline)

[scottdj92]

facebook/react-native#12649