Suggestion for Seeing Changes immediately

Hello!

regarding: https://github.com/demchenkoalex/react-native-module-template#how-to-see-my-changes-immediately-in-the-example

It seems like it works to have:

```
  "main": "lib/index.js",
  "react-native": "src/index.tsx",
```

(shamelessly stolen from react-navigation 😆)