onScroll with AnimatedEvent

**Is your feature request related to a problem? Please describe.**
from this [issue](https://github.com/hyochan/react-native-masonry-list/issues/26) we know that you already update onScroll props.
but i have a question:
1. how to use it, because i dont find it in the docs
2. for using onScroll animation i have to use ref props. this library not support ref props
3. i use AnimatedEvent in onScroll props so we have this error
```
_onScroll is not a function. (In '_onScroll(e)', '_onScroll' is an instance of AnimatedEvent)
```

**Describe the solution you'd like**
1. please add React.forwardRef() so we can using ref props
2. maybe you should use AnimatedEvent.ScrollView