Added "Jump To Content" to implement bypass blocks in example files ready for review

Pull request adds the "Jump To Content" menu button to all examples through the "app.js" file included in every example.

Please review the latest changes so we can get this merged as soon as possible.

Pull Request:
https://github.com/w3c/aria-practices/pull/1860

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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