Add info about aec and parallel APIs to homepage

[elliottower]

Description

Minor PR based on feedback from Discord saying it was confusing figuring out which environments are turn based. May also edit the AEC and Parallel API pages to include info about example envs (e.g., mention that classic has board games, mention that butterfly has parallel pistonball and SISL has parallel multiwalker env for example) and explain them briefly

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.

Fixes # (issue), Depends on # (pull request)

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Screenshots

Please attach before and after screenshots of the change if applicable.
To upload images to a PR -- simply drag and drop or copy paste.

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