fix(useElementHover): support set el ref type

[JiatLn]

Description

const dropZoneRef = ref<HTMLElement>()     // <-- when i set ref as a HTMLElement
function onDrop(files: File[] | null) {
  if (!files)
    return
  const url = window.URL.createObjectURL(files[0])
  gifUrl.value = url
}
const { isOverDropZone } = useDropZone(dropZoneRef, onDrop)
const isHovered = useElementHover(dropZoneRef) // <- it got a type error as follow

<div ref="dropZoneRef">
  xxx
</div>

类型“Ref<HTMLDivElement | undefined>”的参数不能赋给类型“MaybeComputedRef”的参数。
不能将类型“Ref<HTMLDivElement | undefined>”分配给类型“Ref”。

Additional context

---

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

Before submitting the PR, please make sure you do the following

• Read the Contributing Guidelines.
• Read the Pull Request Guidelines.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Ideally, include relevant tests that fail without this PR but pass with it.