[Feature Request] Uploader Support for Folder selection with webkitdirectory attribute

### Existing Component
Yes

### Component Name
el-upload

### Description
This has been mentioned in a couple cases in the past:
https://github.com/ElemeFE/element/issues/13289
https://github.com/ElemeFE/element/issues/14026

But since then it looks like this is in the draft spec: https://wicg.github.io/entries-api/#dom-htmlinputelement-webkitentries
It also seems like this feature has support across most browsers: https://developer.mozilla.org/en-US/docs/Web/API/HTMLInputElement/webkitdirectory

Maybe we could revisit this as it seems like it has become more standardized?

It seems the component already supports multiple files, it would be nice if the multi-file selection could be driven by selecting a folder.