background实现边线动画

边线左侧划出，右侧收起，关键点就是 改变background-position的位置left -> right

.div {
    background: linear-gradient(to right, #ec695c, #61c454) no-repeat right bottom;
    background-size: 0 2px;
    transition: background-size 1.3s;
}

.div:hover {
    background-position-x: left;
    background-size: 100% 2px;
}