Does this package support gymnasium or not?

[ernestum]

The newest release right now is called gymnasium support but looking at the setup.py and other source files, I noticed that

• gymnasium is nowhere used nor is there a dependency to it
• gym is used but there is no dependency to it

Maybe we should

• define what it means to support gymnasium
• Fix the dependencies to at least depend on gym, better depend on gymnasium and ensure compatibility

[simoninithomas]

It does now 😄