scroll-view官方文档：https://mp.weixin.qq.com/debug/wxadoc/dev/component/scroll-view.html
示例1：
<scroll-view scroll-y style="height: 200px;"> <view id="green" class="scroll-view-item bc_green" style='height: 100px;background-color:green'></view> <view id="red" class="scroll-view-item bc_red" style='height: 100px;background-color:red'></view> <view id="yellow" class="scroll-view-item bc_yellow" style='height: 100px;background-color:yellow'></view> <view id="blue" class="scroll-view-item bc_blue" style='height: 100px;background-color:blue'></view> </scroll-view>
