Carousel example review

OK, finally,  the issues obvious to Jon and me in our proposed carousel
example are fixed.

The pull request is ready for review.

PR: 

https://github.com/w3c/aria-practices/pull/958

Example page in feature branch:

https://raw.githack.com/w3c/aria-practices/issue458-add-carousel-example/exa
mples/carousel/carousel-1/carousel-1.html

 

Best,

Matt King