doc(README): mention arguments of onSnapToItem callback
doc(README): mention arguments of onSnapToItem callback

houseofstylist/react-native-snap-carousel,archriss/react-native-snap-carousel,archriss/react-native-snap-carousel,houseofstylist/react-native-snap-carousel,houseofstylist/react-native-snap-carousel,archriss/react-native-snap-carousel,archriss/react-native-snap-carousel