ios底部白条（安全区处理），让背景能够铺满安全区

第一步

1.viewport-fit=cover 重点
<meta name="viewport"
content="width=device-width,initial-scale=1,maximum-scale=1,minimum-scale=1,
user-scalable=no,minimal-ui,viewport-fit=cover"/>

2.body 设置
body {
  height: 100%;
  width: 100%;
  /*overflow-x:hidden;*/
  /*overflow-y: scroll;*/
  /*适配苹果底部白条*/
  padding-top: env(safe-area-inset-top);
  padding-right: env(safe-area-inset-right);
  padding-bottom: env(safe-area-inset-bottom);
  padding-left: env(safe-area-inset-left);
}