You can keyboard-drag an item outside its scrollable container element by holding down the arrow key

I'm been working on porting a sortable list from `@dnd-kit/core` to `@dnd-kit/react`.

Once thing I've noticed is that if you have a DragDropProvider inside a scrollable container element, if you hit Enter to keyboard-drag an item, then hold down the Up or Down arrow key, you can drag the item entirely outside of the container element, presumably because the auto-scroller doesn't respond fast enough to keep up with the arrow key events.

I've made a temporary workaround to throttle arrow key events to no more than one per 100ms, which seems to stop the issue from happening:

```typescript
// During keyboard "dragging", disallow repeated keydown events more frequent than 100ms
// dnd-kit 0.5 has a bug where holding down an arrow key can "drag" an element out of its container.

const timeStampRef = useRef(0);

useEventListener(
document,
"keydown",
(event: Event) => {
const e = event as KeyboardEvent;
if (dragMethod === DragMethod.KEYBOARD && e.key.startsWith("Arrow")) {
// tried 50ms, was too fast
if (e.timeStamp - timeStampRef.current < 100) {
e.stopImmediatePropagation(); // stopPropagtion() isn't enough; dnd-kit also listens on *document*
} else {
timeStampRef.current = e.timeStamp;
}
}
},
true,
);

// Don't apply throttling when user is tapping the key (just when they hold it down)
useEventListener(document, "keyup", () => {
timeStampRef.current = 0;
});
```

(`useEventListener()` is just a hook that calls `addEventListener()` on and `removeEventListener()` on cleanup. `dragMethod` comes from a custom monitor that you see the code for in #2118.)

Reproduce the issue with a DragDropProvider inside a scrollable container: start a keyboard drag with Enter, then hold the Up or Down arrow key. Compare the behavior with the reported 100ms arrow-key throttle workaround. Done means repeated arrow-key events no longer move the dragged item outside its scrollable container while normal key taps still work.

Written by the indexing model from the issue text.