Add timestamp to startup and shutdown commands

src/assets/HestiaClasses.js

@@ -118,14 +118,16 @@ export class Communicator {
     // Send startup command
     startup() {
         this.send('hestia/command/startup', JSON.stringify({
-            "publisher": "front"
+            "publisher": "front",
+            "timestamp": Date.now()
         }));
     }
 
     // Send shutdown command
     shutdown() {
         this.send('hestia/command/shutdown', JSON.stringify({
-            "publisher": "front"
+            "publisher": "front",
+            "timestamp": Date.now()
         }));
     }
 }