iOS: Update diagnostic screen on state update

Summary: Update the diagnostic screen whenever the sonar state changes.

Reviewed By: priteshrnandgaonkar

Differential Revision: D9218765

fbshipit-source-id: 654a35e309cb43df18bc8c8a645d469eddc1031d

iOS/SonarKit/SonarClient.h

@@ -8,6 +8,7 @@
 #import <Foundation/Foundation.h>
 
 #import "SonarPlugin.h"
+#import "FlipperStateUpdateListener.h"
 
 /**
 Represents a connection between the Sonar desktop och client side. Manages the lifecycle of attached
@@ -50,6 +51,11 @@ Get the current state of the sonar client
 */
 - (NSString *)getState;
 
+/**
+Subscribe a ViewController to state update change notifications
+*/
+- (void)subscribeForUpdates:(id<FlipperStateUpdateListener>)controller;
+
 // initializers are disabled. You must use `+[SonarClient sharedClient]` instance.
 - (instancetype)init NS_UNAVAILABLE;
 + (instancetype)new NS_UNAVAILABLE;