fix typo in readme's ios setup instructions

Author: cameron

README.md

@@ -59,7 +59,7 @@ Since `react-native-oauth` depends upon the `RCTLinkingManager` (from react-nati
 In your app, add the following line to your `HEADER SEARCH PATHS`:
 
 ```
-$(SRCROOT)/../node_modules/react-native/Libraries/LinkingiOS
+$(SRCROOT)/../node_modules/react-native/Libraries/LinkingIOS
 ```
 
 ![](./resources/header-search-paths.png)