文档：https://www.uvui.cn/components/intro.html
基础布局,uv-row行，一行以12宽为单位，uv-col栏
html
<uv-row customStyle="margin-bottom: 10px">
<uv-col span="3">
<view class="demo-layout bg-purple"></view>
</uv-col>
<uv-col span="6">
<view class="demo-layout bg-purple-light"></view>
</uv-col>
<uv-col span="3">
<view class="demo-layout bg-purple-dark"></view>
</uv-col>
</uv-row>