Currently, mouseenter/mouseleave pause the carousel, but these listeners are not added if it's a touch-enabled device. This causes problems on touch-enabled laptop/desktop devices, or when a mouse is paired with, say, an Android phone/tablet, as then the mouse listeners are not added and the carousel does not pause as it should when the user interacts with the mouse.
This PR modifies the behavior: mouse listeners are always added. Additionally, on touch devices, an extra touchend listener is included. Mouse users on touch-enabled devices now can pause the carousel as expected. If the user interacts with the carousel with the touchscreen, the carousel is now paused for the duration of this._config.interval (plus an extra 500 milliseconds, just to make sure we always wait until the mouse compat events have definitely been fired - which is what made the original code necessary in the first place since touch events also fire a mouseenter compatibility event), and then the cycling is explicitly restarted.
This now allows touchscreen users some time to read/interact with the carousel slide, before cycling is resumed. And it fixes the broken behavior for mouse users on touch-enabled devices too.
Closes #20847 (closed) (but the problem is not limited to Firefox, same happens on, say, Chrome on a touch-enabled device)