www/py-dj50-channels: New port

Channels augments Django to bring WebSocket, long-poll HTTP, task
offloading and other async support to your code, using familiar Django
design patterns and a flexible underlying framework that lets you not
only customize behaviours but also write support for your own protocols
and needs.

Happy to pass this port to its maintainer who already maintain the
Django 4.2 variant of it.

Co-authored-by: Kai Knoblich <kai@FreeBSD.org>
PR: 283044, 283045 [1]
Reported by: James TD Smith
MFH: 2024Q4 (required to fix [1])