Added docs for location transform
Added docs for location transform

https://github.com/mauron85/background-geolocation-ios/pull/3/
https://github.com/mauron85/background-geolocation-android/pull/8
mauron85/react-native-background-geolocation,mauron85/react-native-background-geolocation,mauron85/react-native-background-geolocation,mauron85/react-native-background-geolocation