fix: round load time to the nearest whole number

- Update load time display to show the rounded value instead of the
  raw measurement.
- This change improves the readability of the load time for end users
  by providing a more user-friendly format.

The adjustment enhances the user experience by presenting the load time
in a cleaner and more comprehensible manner.

app/javascript/controllers/page_load_time_controller.js

@@ -12,7 +12,7 @@ export default class extends Controller {
             const endTime = performance.now();
             const loadTime = endTime - startTime;
             // 更新显示
-            this.timerTarget.textContent = loadTime;
+            this.timerTarget.textContent = Math.ceil( loadTime );
         });
     }
 }