css 新属性 margin-trim、align-content

####margin-trim 去除边上的 margin

.card {
    margin-trim: block; /* Removes from top and bottom */
    margin-trim: inline; /* Removes from left and right */
    margin-trim: block-start block-end; /* Removes from top and bottom */
    margin-trim: inline-start; /* Removes from left */
}

####align-content 直接垂直居中

<div id="app" style="align-content:center;height:200px;border: red solid 1px;">
  <div style="color:red;border: red solid 1px;">垂直居中</div>
</div>