Update security permissions for GitHub workflows

[andrewtanJS]

Description

Following https://github.com/openai/gym/pull/3094, adds explicit permissions for the GitHub workflows for PRs.

Type of change

• New feature (non-breaking change which adds functionality)

Checklist:

• [x] I have run the pre-commit checks with pre-commit run --all-files (see CONTRIBUTING.md instructions to set it up)
• [x] I have run pytest -v and no errors are present.
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] I solved any possible warnings that pytest -v has generated that are related to my code to the best of my knowledge.
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes