DemoUpload()

## Bug report

### Describe the bug

https://www.htmlquick.com/reference/tags/input-file.html
is not valid any more

### How to reproduce

Steps to reproduce the behavior (e.g.):

1. use wd_demo.au3
2. try `DemoUpload`

### Expected behavior

new site + new code with working upload

### Screenshots

none

### Additional context

maybe https://www.file.io/ can be used ?

### System under test

none