Add GetEditorStateAsString in events

public/smartcomponent/svg-layout-designer.ts

@@ -204,6 +204,17 @@
             component.dispatchEvent(new CustomEvent(eventType));
         }
 
+        /**
+         * Return in a callback the current history of the editor as string
+         * @param callback 
+         */
+        public GetEditorStateAsString(callback: (state: string) => void) {
+            const eventType = 'getEditorStateAsString';
+            this.app.AddEventListener(eventType, callback);
+            const component = this.GetEditorComponent();
+            component.dispatchEvent(new CustomEvent(eventType));
+        }
+
         /**
          * Set the current history of the editor
          * @param history Whole history of the editor