StrEnum. _generate_next_value_ in future/input

[cdeil]

When I opened Arcade in PyCharm it flagged this as "improper first parameter":

https://github.com/pythonarcade/arcade/blame/cdd6f66aef330856a84446f8a34d176b7e66c2f5/arcade/future/input/inputs.py#L40

I'm not familiar with this, but in the Python std lib I see this:

https://docs.python.org/3/library/enum.html#enum.StrEnum

https://github.com/python/cpython/blob/0468ea12305ef5a0a3d1dc4af8a82fb94d202cd6/Lib/enum.py#L1377-L1382

Probably the current implementation of StrEnum in Arcade doesn't work, this has to be a staticmethod?

What to do? Remove the method? Copy over std lib implementation?

cc @Cleptomania

[einarf]

It definitely states that it's a staticmethod but it works because *_ consumes all parameters including self.

[einarf]

Fixed + unbroke the experimental input example using old spritelist api.