Add Training Tutorial and CITATION.cff

[BolunDai0216]

Description

Added a training tutorial using StableBaselines3 to the website and added a CITATION.cff file for easy citation.

Type of change

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

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