Adding isSubscribed to the OSEmailSubscriptionState dictionary

Author: emawby

iOS_SDK/OneSignalSDK/Source/OSEmailSubscription.m

@@ -95,7 +95,8 @@ - (void)setEmailAddress:(NSString *)emailAddress {
 - (NSDictionary *)toDictionary {
     return @{
        @"emailUserId": _emailUserId ?: [NSNull null],
-       @"emailAddress": _emailAddress ?: [NSNull null]
+       @"emailAddress": _emailAddress ?: [NSNull null],
+       @"isSubscribed": @(self.isSubscribed)
     };
 }