Added missing method for flash toggling on iOS

Author: marqroldan

index.d.ts

@@ -128,6 +128,7 @@ declare module "react-native-twilio-video-webrtc" {
     connect: (options: iOSConnectParams | androidConnectParams) => void;
     disconnect: () => void;
     flipCamera: () => void;
+    toggleFlash: () => void;
     toggleSoundSetup: (speaker: boolean) => void;
     getStats: () => void;
     publishLocalAudio: () => void;

src/TwilioVideo.ios.js

@@ -213,6 +213,13 @@ export default class TwilioVideo extends Component {
     TWVideoModule.flipCamera()
   }
 
+  /**
+   * Toggle Torch functionality
+   */
+   toggleFlash () {
+    TWVideoModule.toggleFlash()
+  }
+
   /**
    * Toggle audio setup from speaker (default) and headset
    */