docs: h5 demo qrcode

docs/README.md

@@ -23,7 +23,7 @@
       </a>
       <a href="https://hellouniapp.dcloud.net.cn/" target="_blank" class="clear-style barcode-view">
         <div class="barcode-img-box">
-          <img src="https://img-cdn-qiniu.dcloud.net.cn/uniapp/doc/uni-h5.png" width="160" />
+          <img src="https://img.cdn.aliyun.dcloud.net.cn/guide/uniapp/uni-h5-hosting-qr.png" width="160" />
         </div>
         <b>H5版</b>
       </a>