關於 iphone H5劉海屏適配

默認劉海屏的webview是有安全區域的，加上viewport-fit=cover屬性后webview會全屏，全屏后為了適配劉海屏加上安全區域

padding-top: 1rem;//android樣式

padding: env(safe-area-inset-top) env(safe-area-inset-right) env(safe-area-inset-bottom) env(safe-area-inset-left);// ios 樣式

padding: constant(safe-area-inset-top) constant(safe-area-inset-right) constant(safe-area-inset-bottom) constant(safe-area-inset-left); // ios樣式

ios兩個樣式原因
when the iPhone X first came out, it used  constant() instead of  env(), but as of 11.2,  constant() has been removed in favor of the standardized  env()