Updated CustomEnvironment tutorial comments

[GiovanniGrotto]

Description

I added some comments to the CustomEnvironment prisoner tutorial

Type of change

• 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 run pytest -v and no errors are present.
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I solved any possible warnings that pytest -v has generated that are related to my code to the best of my knowledge.
• 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

[elliottower]

These are great thanks. One comment though is to make sure it's clear which of the bullet points are true for all environments, and which are specific for this environment. You had things about prisoner positions and such in the same list as termination truncation etc, probably best to just say something like "the reset method must do the following" and then specify this environment itself does some more additional steps.

But this is much improved so thanks a ton for the help