Added screens in sample app for notification

Summary:
Added a basic communication flows and a button to trigger notification
{F142016937}

Reviewed By: jknoxville

Differential Revision: D10492428

fbshipit-source-id: b65fc46b3be695852f9197771a253d9e8596f328

iOS/Plugins/FlipperKitExamplePlugin/FlipperKitExamplePlugin/FlipperKitExamplePlugin.h

@@ -8,7 +8,12 @@
 #import <Foundation/Foundation.h>
 #import <FlipperKit/FlipperPlugin.h>
 
+@protocol FlipperKitExampleCommunicationResponderDelegate
+- (void)messageReceived:(NSString *)msg;
+@end
+
 @interface FlipperKitExamplePlugin : NSObject<FlipperPlugin>
+@property (weak, nonatomic) id<FlipperKitExampleCommunicationResponderDelegate> delegate;
 
 - (instancetype)init NS_UNAVAILABLE;
 - (void)sendMessage:(NSString *)msg;