Add support for a type-safe routing

[jferrettiboke]

It'd be great to add support for a type-safe routing. Something similar to nextjs-routes.

[EvanBacon]

We've talked about doing this. Will probably not get around to it until the beta has been completed.

[Zeko369]

Would you be interested in contributions for this?

[EvanBacon]

Seems like a difficult and opinionated project that will probably be implemented using file watching and AST parsing in Expo CLI. Probably best if I handle it personally, but feel free to give it a shot.

[sandulat]

@EvanBacon Related #448