Typo on slim-underline() mixin

[ricardozea]

Hello,

There's a typo on your slim-underline() mixin.

The mixin says @mixin slim-underline() but the 'usage' example in the comment says // Usage: @include slime-underline;

slim on one and slime on the other.

https://github.com/jquery/css-chassis/blob/master/scss/atoms/typography/_mixins.scss