Codepen addition ready for review on 6 example pages

Hi all,

 

We need at least one reviewer for a PR where Valerie has finished the
CodePen button work for 6 example pages. Please have a look at:

https://github.com/w3c/aria-practices/pull/1532

 

It should be a pretty quick review to double check the button is showing up,
positioned correctly,  and functioning as it should on those 6 pages.

 

There will be more PRs for adding CodePen coming. We're breaking it into
small groups to facilitate quick reviews.

 

Thanks!

Matt