refine: uv-ui style

src/pages/demo/base/uv-ui.vue

@@ -7,7 +7,9 @@
 <template>
   <view class="mt-10">
     <uv-button type="primary">button</uv-button>
-    <uv-qrcode ref="qrcode" class="m-auto" size="300px" value="https://h5.uvui.cn"></uv-qrcode>
+    <view class="center mt-8">
+      <uv-qrcode ref="qrcode" size="300px" value="https://h5.uvui.cn"></uv-qrcode>
+    </view>
   </view>
 </template>