Fix outdated docs for TimeLimit max_episode_steps and add validation.

[troiganto]

Description

• update docstring of TimeLimit.__init__()
• add assert isinstance(max_episode_steps, int) and max_episode_steps > 0
• I assume max_episode_steps==0 can be safely disallowed?
• add tests for both assertions

Fixes #1147

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• I have run the pre-commit checks with pre-commit run --all-files (see CONTRIBUTING.md instructions to set it up)
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[troiganto]

Hrm. These errors look very interesting but also unrelated to my changes. Most seem to be type disagreements in the spaces package.

[pseudo-rnd-thoughts]

Thanks for the PR, looks good

[pseudo-rnd-thoughts]

The doctest seem to be failed for unrelated reasons