Upload: drop zone didn't handle any accept config

### Description

The `accept` config can't work with drag and drop upload.

### Reproduce Steps

1. Set `accept="image/*"` to the component;
2. Set `drag` as true;
3. Drop a PDF file into the zone;
4. The PDF file uploaded.

### Solution

Should do some check when drop event happened. Even more consideration like hint when `dragenter` event for better user experience.

And the temporary workaround is to check the type by developer self in `beforeUpload` handler.