feat: add syncCurrentState to sync registration and call state

ios/Classes/LiblinphoneFlutterPlugin.swift

@@ -206,6 +206,10 @@ public class LiblinphoneFlutterPlugin: NSObject, FlutterPlugin {
             linphoneBridge.stop()
             result(true)
 
+        case "syncCurrentState" :
+            linphoneBridge.syncCurrentState()
+            result(true)
+            
         default:
             result(FlutterMethodNotImplemented)
         }

ios/Classes/LinphoneBridge.swift

@@ -244,6 +244,11 @@ class LinphoneBridge {
             return .audio
         }
     }
+
+    func syncCurrentState() {
+        onRegistrationStateChanged(registrationState.rawValue)
+        onCallStateChanged(callState.rawValue)
+    }
 }
 
 // MARK: - CoreDelegate