Add react-native-web to the example app

[hectahertz]

The example folder of this repo contains an Expo app with examples for both iOS and Android, but there's nothing for web yet.

For now I'm just using this fork of a boilerplate for quick manual testing, but it's not a great long term solution.

An option would be to fully transform the example app into something similar to the boilerplate but we lose the possibility of deploying it to expo which I find very useful.

Another option would be to just share the components and screens and have two separate apps, this would probably fit this use case better.