利用safe-area-inset-*兼容iPhone刘海屏
分别创建屏幕上边框，右边框，下边框，左边框安全距离：safe-area-inset-top，safe-area-inset-right，safe-area-inset-bottom，safe-area-inset-left使用：iOS 11padding-top: constant(safe-area-inset-top);padding-right: constant(safe-area-inset-right);padding-bottom: constant(safe-area-in
