Created by: ramiy
The Beta version removed all the .hidden- classes. They where replaced with d-*-none classes. But no docs can be found in https://getbootstrap.com/docs/4.0/utilities/display/
This PR adds a new section how to hide elements. This is section should replace the Alpha version docs for hidden-* class found in https://v4-alpha.getbootstrap.com/layout/responsive-utilities/
More info about the change can be found in the migration docs https://getbootstrap.com/docs/4.0/migration/#responsive-utilities