refactor: update demo observer

Author: jorenrui

demo/observer.html

@@ -34,9 +34,10 @@
       <li>
         <button
           :click="this.parentNode.parentNode.removeChild(this.parentNode)"
-          :text="`look at my id list item (click to delete)`"
+          :text="`my id is ${this.getAttribute('id')} (not changing on hover anymore) list item (click to delete)`"
           :mouseenter="el.isHovered = true"
           :mouseleave="el.isHovered = false"
+          id="originalID"
           :class="el.isHovered ? 'bg-red-200' : ''"
         ></button>
         <button