introduce interfaces for state/feedback topics

src/AItem.ts

@@ -3,6 +3,15 @@ import { mqttHandler } from './MqttDispatcher'
 import { ExportType } from './Export'
 
 
+
+export interface HasStateTopic {
+    getStateTopic() : string
+}
+
+export interface HasStateAndFeedbackTopic extends HasStateTopic {
+    getStateFeedbackTopic() : string
+}
+
 export abstract class AItem {
     protected topicFirstPart: string
     protected itemId: string