Add watchOS support for SwiftDuxExtras

Author: kamilpowalowski

Sources/SwiftDuxExtras/Persistence/PersistStateMiddleware.swift

@@ -2,7 +2,12 @@ import Combine
 import Foundation
 import SwiftDux
 
-#if canImport(UIKit)
+#if canImport(WatchKit)
+
+ import WatchKit
+ fileprivate let notification: NSNotification.Name? = WKExtension.applicationDidEnterBackgroundNotification
+
+#elseif canImport(UIKit)
 
  import UIKit
  fileprivate let notification: NSNotification.Name? = UIApplication.didEnterBackgroundNotification