docs(Embedding iOS): Added swift code for embedding react-native in an app

Summary: Closes https://github.com/facebook/react-native/pull/4198

Differential Revision: D3075219

Pulled By: mkonicek

fb-gh-sync-id: c350a4074e4ee586804c48b9587135f3fce7b243
shipit-source-id: c350a4074e4ee586804c48b9587135f3fce7b243

docs/EmbeddedAppIOS.md

@@ -118,6 +118,7 @@ In a view controller that wants to manage this view, go ahead and add an outlet
 @property (weak, nonatomic) IBOutlet ReactView *reactView;
 @end
 ```
+__NOTE__ For Swift apps there is no need for that.
 
 Here I disabled **AutoLayout** for simplicity. In real production world, you should turn on AutoLayout and setup constraints by yourself.
 
@@ -149,6 +150,34 @@ Then add it as a subview of the `ReactView`.
 rootView.frame = self.bounds;
 ```
 
+### Swift apps
+
+Add the following to ReactView.swift file:
+
+```
+import UIKit
+import React
+
+class ReactView: UIView {
+
+  let rootView: RCTRootView = RCTRootView(bundleURL: NSURL(string: "http://localhost:8081/index.ios.bundle?platform=ios"),
+    moduleName: "SimpleApp", initialProperties: nil, launchOptions: nil)
+    
+  override func layoutSubviews() {
+    super.layoutSubviews()
+
+    loadReact()
+  }
+  
+  func loadReact () {
+        addSubview(rootView)
+        rootView.frame = self.bounds
+  }
+}
+```
+
+And then make sure your view is added in a ViewContainer or story board file.
+
 ## Start Development Server
 
 In root directory, we need to start React Native development server.