[Feature Request] Support VMenu arrow key navigation when in shadow root

[smaatcoda]

Problem to solve

Currently the arrow key navigation is broken if vuetify is running in shadow dom.

Proposed solution

Instead of using document in the src/util/helpers.ts:435-464

export function getNextElement(elements, location, condition) {
  let _el;
  let idx = elements.indexOf(document.activeElement);
  const inc = location === 'next' ? 1 : -1;
  do {
    idx += inc;
    _el = elements[idx];
  } while ((!_el || _el.offsetParent == null || !(condition?.(_el) ?? true)) && idx < elements.length && idx >= 0);
  return _el;
}
export function focusChild(el, location) {
  const focusable = focusableChildren(el);
  if (!location) {
    if (el === document.activeElement || !el.contains(document.activeElement)) {
      focusable[0]?.focus();
    }
  } else if (location === 'first') {
    focusable[0]?.focus();
  } else if (location === 'last') {
    focusable.at(-1)?.focus();
  } else if (typeof location === 'number') {
    focusable[location]?.focus();
  } else {
    const _el = getNextElement(focusable, location);
    if (_el) _el.focus();else focusChild(el, location === 'next' ? 'first' : 'last');
  }
}

the active element could be looked up on a more generic scope:

  const scope = el.getRootNode();
  ...
  let idx = elements.indexOf(scope.activeElement);