Adds visualization and simple policy step to getting started docs on custom MARL env

[marimeireles]

Description

Hello!
This is a small contribution I've wrote for myself but folks in the Discord said they were interested in having it upstream. I'm adding random policy and a simple visualization to the environment creation tutorial.

Here are some things I've noticed you might want changed:

• There's a "ghost" empty file over there, 5. Should I keep it as it is or remove it and rename my additions to be 5?
• I've also notice you have much longer docs in the previous classes. I can write more extensive doc strings in the code if you think it's needed.

Type of change

Docs

Screenshots

Nothing too fancy:

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

[dm-ackerman]

This looks cool. I know Elliot has talked about wanting to expand the tutorials.

Is it possible to implement what you have as part of the render function and then use the interaction loop used elsewhere in the docs?
I'm wondering if that might be a good approach.

[elliottower]

The image looks fine and I like the idea, but we want all the code to be as simple and similar as possible, so you should try to use the same functionality as seen in other example envs (using render() as David says, and not making new functions like run, basically make it the same as any other official environment and then when people go through the tutorial, they will understand the structure of base environments as well

[elliottower]

I’ve been pretty busy so haven’t had a chance to look at discord or many things on here in a few weeks. Maybe @dm-ackerman could look subsequent versions of this over/help with suggestions and such, and then send me a message when to look at the finished product and approve it?

[elliottower]

Hey, if you're still interested in helping out with this let me know