PyQt5 Wheels for Apple Silicon

[Phil Thompson]

The local PyPI server (https://www.riverbankcomputing.com/pypi/) now has 
PyQt5 snapshot wheels and PyQt5-Qt5 Qt wheels for Apple Silicon. I 
haven't had a chance to test these yet and they are "experimental". They 
are based on Qt v5.15.10 and I intend at some point to upload Linux and 
Windows Qt wheels using that version.

There is also a Qt5 v5.15.10 wheel for Apple Intel Macs.

Feedback please.

Phil