multimedia/uxplay: add new port

UxPlay is an AirPlay2 Mirror server. Its main use is to act like an
AppleTV for screen-mirroring (with audio) of iOS/iPadOS/macOS clients
(iPhone, iPod Touch, iPad, Mac computers) in a window on the server
display (with the possibility of sharing that window on screen-sharing
applications such as Zoom). UxPlay supports Apple's AirPlay2 protocol
using "Legacy Pairing".

The UxPlay server and its client must be on the same local area network,
on which a Bonjour/Zeroconf mDNS/DNS-SD server is also running (only
DNS-SD "Service Discovery" service is strictly necessary, it is not
necessary that the local network also be of the ".local" mDNS-based
type). This is usually provided by Avahi, through the avahi-daemon
service.