Integrate Pygame Zero REPL into Mu

[r0the]

The newest version of Pygame Zero supports an optional REPL feature. It would be nice to have that integrated into Mu's Pygame Zero mode.

https://pygame-zero.readthedocs.io/en/latest/repl.html

Here's how to install:

https://pygame-zero.readthedocs.io/en/latest/installation.html#installing-the-repl

[carlosperate]

@ntoll I believe this is something you wanted to do as well? In that case I'll mark this for the v1.2 milestone.