Created by: DavidDeSloovere
If media-breakpoint-down(xl) is not listed, then media-breakpoint-up(xs) does not need to be listed either. The above 4 media queries are now aligned with the 4 media-breakpoint-up mixins (just like their media-breakpoint-down counterparts).
Also added example for media-breakpoint-down.
This PR is a result of questions from a colleague that misinterpreted the existing docs. This should clarify it.