ported demo to stackblitz.com

Author: abulka

demo/vue3js_dynamic-modern-renderCB.html

@@ -21,6 +21,7 @@ <h1>Vue3: Gridstack Controls Vue Rendering Grid Items</h1>
       Helpful Resources:
     <ul>
       <li><a href="https://vuejs.org/guide/extras/render-function.html#render-functions-jsx" target="_blank">Vue Render Functions</a></li>
+      <li><a href="https://stackblitz.com/edit/vitejs-vite-phhdkeju" target="_blank">This Demo as a Vue SFC on Stackblitz</a></li>
     </ul>
     </p>
     <button type="button" @click="addNewWidget">Add Widget</button> {{ info }}