message: Use css transition to create submenu open delay instead of js
diff: -/* eslint-disable no-console */
  /*
  * Copyright 2021 The Backstage Authors
  *
  @@ -55,6 +54,7 @@ const useStyles = (props: { left: number }) =>
  scrollbarWidth: 'none',
  cursor: 'default',
  width: submenuConfig.drawerWidthClosed,
  + transitionDelay: `${submenuConfig.defaultOpenDelayMs}ms`,
  '& > *': {
  flexShrink: 0,
  },
  @@ -98,20 +98,11 @@ export const SidebarSubmenu = (props: SidebarSubmenuProps) => {
  const { isHoveredOn } = useContext(SidebarItemWithSubmenuContext);
  const [isSubmenuOpen, setIsSubmenuOpen] = useState(false);
  - const hoverTimerRef = useRef<number>();
  useEffect(() => {
  - if (hoverTimerRef.current) {
  - clearTimeout(hoverTimerRef.current);
  - hoverTimerRef.current = undefined;
  - }
  - if (isHoveredOn) {
  - hoverTimerRef.current = window.setTimeout(() => {
  - hoverTimerRef.current = undefined;
  - setIsSubmenuOpen(true);
  - }, submenuConfig.defaultOpenDelayMs);
  - }
  + setIsSubmenuOpen(isHoveredOn);
  }, [isHoveredOn]);
  +
  return (
  <div
  className={classnames(classes.drawer, {
  