Updated the ARIA APG example index and coverage report

I received some feedback from Sara and also did some more reviewing on my own on the updated example index and coverage report, so I have made some updates.

Please review and comment on the latest changes:
Preview of example index<https://raw.githack.com/w3c/aria-practices/update-example-index/examples/index.html>
Preview of coverage report<https://raw.githack.com/w3c/aria-practices/update-example-index/coverage/index.html> (Not: the coverage report is only for the internal consumption of the working group)
Pull request #1859 for comments on example index and coverage report<https://github.com/w3c/aria-practices/pull/1859>

Thank you,
Jon

Jon Gunderson, Ph.D., CPWA (he/him/his)
Coordinator of Accessible IT Group
University of Illinois at Urbana/Champaign
1207 S. Oak Street
Champaign, IL 61820

Phone: (217) 244-5870
E-mail: jongund@illinois.edu<mailto:jongund@illinois.edu?Subject=Re%3A%20Alternative%20date%20combobox%20grid%20date%20picker%20example%20for%20ARIA%20APG&In-Reply-To=%3CBYAPR11MB3413C2168E1DF82F6E4C7B2CC8BE0%40BYAPR11MB3413.namprd11.prod.outlook.com%3E&References=%3CBYAPR11MB3413C2168E1DF82F6E4C7B2CC8BE0%40BYAPR11MB3413.namprd11.prod.outlook.com%3E><mailto:jongund@illinois.edu<mailto:jongund@illinois.edu?Subject=Re%3A%20Alternative%20date%20combobox%20grid%20date%20picker%20example%20for%20ARIA%20APG&In-Reply-To=%3CBYAPR11MB3413C2168E1DF82F6E4C7B2CC8BE0%40BYAPR11MB3413.namprd11.prod.outlook.com%3E&References=%3CBYAPR11MB3413C2168E1DF82F6E4C7B2CC8BE0%40BYAPR11MB3413.namprd11.prod.outlook.com%3E>>
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