message: Support DOM nodes that contain focusable elements being added to a focus zone.
diff: @@ -446,12 +446,12 @@ export function focusZone(container: HTMLElement, settings?: FocusZoneSettings):
  for (const mutation of mutations) {
  for (const addedNode of mutation.addedNodes) {
  if (addedNode instanceof HTMLElement && isFocusable(addedNode)) {
  - beginFocusManagement(addedNode)
  + beginFocusManagement(...iterateFocusableElements(addedNode))
  }
  }
  for (const removedNode of mutation.removedNodes) {
  if (removedNode instanceof HTMLElement && savedTabIndex.has(removedNode)) {
  - endFocusManagement(removedNode)
  + endFocusManagement(...iterateFocusableElements(removedNode))
  }
  }
  }
  