Firefox currently seems extremely fickle - with `pan-y` if fires pointercancel as soon as a touch strays even a pixel or so vertically.
While `touch-action: pan-y` would be ideal (allowing users to scroll the page even when their finger started the scroll on the carousel), this prevents a swipe that isn't perfectly/only horizontal to be recognised by Firefox.

in particular, no need to use originEvent, and preventDefault() only needed for touch events

these may also be the cause of weird behavior in Chrome/Surface, where scrolling vertically triggers slide advance

- my fault, my original advice of using `touch-action: pan-x` is exactly the value we *don't* want to have the browser handle...

Broken after 787441d4.

adds the ability to assign data-interval to an individual carousel-item

see: https://github.com/twbs/bootstrap/issues/26847
in v4, destroy was replaced by dispose

With the current docs directory setup, I'm making too many mistakes and have to manually address path changes and directory moves on deploy. This makes for a frustrating experience developing locally and shipping releases. With this PR, we're basically back to the same setup from v3—duplicating the dist directory into our docs directory. Not the most ideal, but very straightforward for me as the release manager.