[Dependencies] Gymnasium Version

[TheEimer]

As far as I can see, the gymnasium version isn't set in the dependencies. This is likely a problem since we want to be sure if lower than 1.0 or higher is installed due to breakage.

[jmtoepperwien]

I overlooked this issue. I have written down some insights into how to get Gymnasium >=1.0 (and if wanted both) running in #108.
I have also opened a PR to constrain to <1.0, as all code should be fine then (#109).