docs: update add accept info, close #5986

Author: tangjinzhou

components/upload/index.en-US.md

@@ -44,7 +44,7 @@ Uploading is the process of publishing information (web pages, text, pictures, v
 | previewIcon | custom preview icon | v-slot:iconRender="{file: UploadFile}" | - | 3.0 |  |
 | progress | Custom progress bar | [ProgressProps](/components/progress/#API) (support `type="line"` only) | { strokeWidth: 2, showInfo: false } | 3.0 |  |
 | removeIcon | custom remove icon | v-slot:iconRender="{file: UploadFile}" | - | 3.0 |  |
-| showUploadList | Whether to show default upload list, could be an object to specify `showPreviewIcon`,  `showRemoveIcon` and `showDownloadIcon` individually | Boolean or { showPreviewIcon?: boolean, showRemoveIcon?: boolean, showDownloadIcon?: boolean } | true | showDownloadIcon(3.0) |  |
+| showUploadList | Whether to show default upload list, could be an object to specify `showPreviewIcon`, `showRemoveIcon` and `showDownloadIcon` individually | Boolean or { showPreviewIcon?: boolean, showRemoveIcon?: boolean, showDownloadIcon?: boolean } | true | showDownloadIcon(3.0) |  |
 | supportServerRender | Need to be turned on while the server side is rendering. | boolean | false |  |  |
 | withCredentials | ajax upload with cookie sent | boolean | false |  |  |
 
@@ -110,6 +110,10 @@ When uploading state change, it returns:
 - You can consult [jQuery-File-Upload](https://github.com/blueimp/jQuery-File-Upload/wiki#server-side) about how to implement server side upload interface.
 - There is a mock example of [express](https://github.com/react-component/upload/blob/master/server.js) in rc-upload.
 
+### How to select albums or folders on mobile devices?
+
+You can set `:accept="null"`
+
 ### I want to display download links.
 
 Please set property `url` of each item in `fileList` to control content of link.

components/upload/index.zh-CN.md

@@ -110,6 +110,10 @@ cover: https://gw.alipayobjects.com/zos/alicdn/QaeBt_ZMg/Upload.svg
 - 服务端上传接口实现可以参考 [jQuery-File-Upload](https://github.com/blueimp/jQuery-File-Upload/wiki#server-side)。
 - 如果要做本地 mock 可以参考这个 [express 的例子](https://github.com/react-component/upload/blob/master/server.js)。
 
+### 手机设备如何选择相册或文件夹？
+
+你可以设置 `:accept="null"`
+
 ### 如何显示下载链接？
 
 请使用 fileList 属性设置数组项的 url 属性进行展示控制。