Compatibility with jQuery 4

[markfullmer]

Summary

For usage with jQuery 4, this library should be modified to remediate deprecations.

Audit

• Our team performed a machine-based audit of potential deprecations in the slick.js library, checking for items listed in https://blog.jquery.com/2024/02/06/jquery-4-0-0-beta/
• This audit correctly identified the deprecated usage of $.type(), removed in jQuery 4. The recommended remediation is to replace with the JavaScript typeof syntax.
• The audit flagged usage of other elements -- push(), sort(), splice(), focus(), and proxy(). Each of these were evaluated by a human and determined to be JavaScript implementations, not jQuery.
• Our team also compared proposed changes in the original Slick library for jQuery compatibility. See jquery .type() deprecated kenwheeler/slick#4071 and Updates for jQuery 3.0+ and deprecations kenwheeler/slick#4221 . Both of these also flagged $.type() as the main functional change needed. The other changes proposed there do not appear to be required for jQuery 4 compatibility

Testing methodology

1. Our team started with a working implementation of the Accessible 360 Slick library using jQuery 3.
2. We then switched only the underlying jQuery library to jQuery 4.0.0-beta2 and confirmed that the Slick implementation now broke, with a console error Uncaught TypeError: d.type is not a function.
3. We then switched to the remediated version of the Accessible 360 Slick library and confirmed that the implementation was working again and there were no console errors or notices.