Export v4 Util class to make it usable in custom JS functions

Created by: wasinger

For custom transition effects I currently use the transition helper functions $.fn.emulateTransitionEnd and $.support.transition from Bootstrap 3.

While porting my code to Bootstrap 4 I noted that while $.fn.emulateTransitionEnd is still available and works as expected, the $.support.transition function is no longer availabe because it got replaced by Util.supportsTransitionEnd(). Unfortunately, the Util class is available within a Closure only so I cannot access it from my code.

So I ask to export the Util class to the global or jQuery namespace (e.g. as $.BootstrapUtil) to make it available for use in custom JS code.

This is somehow related to #18136 (closed) which complains about the Util class being exported as Util in the global namespace, which is not true for the default build - it is not exported at all, but IMHO should be exported under some name other than plain "Util".