Update StackMonkey.ps1

StackMonkey.ps1

@@ -830,7 +830,11 @@ $style = @'
       }, 10_000);
     });
 
-
+    // when the browser window is closed (X), notify the server to quit
+    window.addEventListener('beforeunload', () => {
+      // keepalive: true ensures the request is sent even as the page unloads
+      fetch('/quit', { method: 'GET', keepalive: true });
+    });
 
     </script>