Fix formatting in ios installation documentation (#2242)

docs/installation-ios.md

@@ -20,6 +20,6 @@
     - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { ... }
     ```
 
-Its content must be replaced with the content of this [reference](https://github.com/wix/react-native-navigation/blob/master/example/ios/example/AppDelegate.m)
+    Its content must be replaced with the content of this [reference](https://github.com/wix/react-native-navigation/blob/master/example/ios/example/AppDelegate.m)
 
-Replace `@"index.ios"` with `@"index"` if you are using `index.js` as your entry point instead of `index.ios.js` and `index.android.js` (it is the default since React Native 0.49).
+    Replace `@"index.ios"` with `@"index"` if you are using `index.js` as your entry point instead of `index.ios.js` and `index.android.js` (it is the default since React Native 0.49).