1.2.post5 + allowing PyGame2

Upstream pgzero was limited to pygame v1.x, which does not have wheels for the latest Python versions. This commit on top of the 1.2.post5 release reduces this restriction so that pygame v2.x can be used.

The wheel hosted here is not really necessary, as this fork can be pip installed via git URL, but it is useful for another Mu workaround to a different issue: mu-editor/mu#1290