mergeLonghand
Collapses longhand properties into the shorthand representation, and where possible will also collapse top/right/bottom/left values. Supports `margin`, `padding` & `border` longhands.
Example
Input
.box {
margin-top: 10px;
margin-right: 20px;
margin-bottom: 10px;
margin-left: 20px;
}Output
.box {
margin: 10px 20px;
}