Auto AV scanning (ClamAV) for uploaded files

**Describe the idea / solution you'd like**
It'd be nice if copyparty has the ability to invoke ClamAV when uploading files. Maybe show a notification based on ClamAV exitcode if file is rejected?

**Describe any alternatives you've considered**
I looked at the available hooks and pondered if I could do it... unfortunately, I'm too dum dum to make such magic happen (Python is alien to me, I should study moar).

**Additional context**
As stopgap measure I made an ugly external fswatch scripthingie to monitor & scan new files in shared folders. Sometimes I use copyparty at retro LANparties, where people might (nope: WILL) share infected stuff. This way malicious files get obliterated before they reach some poor, unsuspecting WinXP potato. But yeah, jokes aside it might be a cool addition.