模拟网络延迟加载，添加正在加载中图标显示

<view>
<!-- 搜索框开始 -->
    <SearchBar></SearchBar>
    <!-- 搜索框结束 -->

    <!-- 轮播图开始 -->
    <view class="index_swiper">
        <swiper autoplay circular indicator-dots>
            <swiper-item 
            wx:for="{
   {swiperList}}"
            wx:for-item="swiper"
            wx:key="id"
            >
                <navigator url="/pages/product_detail/index?id={
   {swiper.id}}">
                    <image src="{
   {baseUrl+'/image/swiper/'+swiper.swiperPic}}" mode="widthFix"/>
                </navigator>
            </swiper-item>
        </swiper>
    </view>
    <!-- 轮播图结束 -->

    <!-- 商品大类显示开始 -->
        <view class="index_bigType">
        <view