WIP: introduces compatibility with gymnasium

[marimeireles]

Turns out the work was really simple!

This is a WIP because a few features are missing even though the overall software seems to be working fine:

• update setup.py/requirements with new reqs.
• currently I'm calling the make function directly in the environment files env = gymnasium.make("HIV-v0", apply_api_compatibility=True), this is not ideal and we should try to keep ourselves within the last API as much as possible. The reason why I'm calling there is because I don't seem able to call make in a file. I'm not entirely sure why but somehow the environment is not registered within gymnasium. If one runs:

import gymnasium as gym

envs = gym.envs.registry.all()
for env in envs:
    print(env)

The gymnasium default environments are all listed but the whynot custom ones are not.
When I run make within an environment it works fine.

• a new version of whynot should be released before merging this PR as we want to have a final version that works for sure with gym and then a new version that's up to date with gymnasium

[marimeireles]

This is the line I have to add so gymansium understands the environment was defined.
As mentioned in the PR body I'm not sure how to register new environments with the gymnasium API. It's a next step.