给input边框和背景颜色设置全透明，但是里面的字不会消失
1.让背景颜色变透明(二选一)
background-color:rgba(0,0,0,0);
background:rgba(0,0,0,0);
2.让边框变透明(二选一)
border-color: transparent;
border: 1px solid rgba(0,0,0, 0);
3.css3文字渐变
color:#DA0A0A;
background-image: -webkit-gradient(linear, 0 0, 0 bottom, from(rgba(248, 0, 0, 1)), to(rgba(95, 4, 4, 1)));
-webkit-background-clip: text;
-webkit-text-fill-color: transparent;