Css设置背景blend mode

使用@supports设置只有在浏览器支持下才开启属性：

@supports( mix-blend-mode: multiply ) {

	.page-header__image::before {
		background: #B3945D;
		opacity: .8;
		mix-blend-mode: multiply;

		content: '';
		display: block;
		width: 100%;
		height: 100%;
		position: absolute;
		top: 0;
		left: 0;
		z-index: 2;
	}
}