react-native 0.60 auto-linking doesn't work for iOS

I started looking into this when I got the same error mentioned here #703

React-Native 0.60 introduced "auto-linking" native modules. This module auto-links correctly in Android but no in iOS which required me to manually add this to my podfile `pod 'RNFS', :path => '../node_modules/react-native-fs'`. React-Native 0.60 also ships with Cocoa Pods so perhaps this lib should be updated to reflect the auto-linking feature in latest RN as well as Cocoa Pods.