docs(use-current-state): add docs for functional initializer mode

fix(dropdown): update layout when mouseenter triggered

components/shared/dropdown.tsx

@@ -1,4 +1,4 @@
-import React, { MutableRefObject, useState } from 'react'
+import React, { MutableRefObject, useEffect, useState } from 'react'
 import { createPortal } from 'react-dom'
 import usePortal from '../utils/use-portal'
 import useResize from '../utils/use-resize'
@@ -57,6 +57,15 @@ const Dropdown: React.FC<React.PropsWithChildren<Props>> = React.memo(
     useDOMObserver(parent, () => {
       updateRect()
     })
+    useEffect(() => {
+      if (!parent || !parent.current) return
+      parent.current.addEventListener('mouseenter', updateRect)
+      /* istanbul ignore next */
+      return () => {
+        if (!parent || !parent.current) return
+        parent.current.removeEventListener('mouseenter', updateRect)
+      }
+    }, [parent])
 
     const clickHandler = (event: React.MouseEvent<HTMLDivElement>) => {
       event.stopPropagation()