Added ELO Rating System Doc

[simoninithomas]

Hello,

Proposed change(s)

• I wrote a small doc about ELO rating system, I think it can help people who want to build multi-agents environments in ML-Agents to grasp rapidly what is ELO.

• The first part is directly taken from your Blogpost, I added the second that explains ELO with mathematical formulas and a simple example.

Have a nice day,

Types of change(s)

• [ ] Bug fix
• [ ] New feature
• [ ] Code refactor
• [ ] Breaking change
• [X] Documentation update
• [ ] Other (please describe)

Checklist

• [ ] Added tests that prove my fix is effective or that my feature works
• [ ] Updated the changelog (if applicable)
• [X] Updated the documentation (if applicable)
• [ ] Updated the migration guide (if applicable)

Other comments

[CLAassistant]

All committers have signed the CLA.

[miguelalonsojr]

hey @simoninithomas , thanks for the contribution! Can you make sure to rebase/merge main, resolve conflicts, and push? That should trigger our latest CI/CD. Once you get to that point, can you update the proposed documentation for the latest version on main? Thanks again!

[simoninithomas]

I updated based on what you asked ✅. Sorry for the big delay I was cleaning the notifications today and I saw this one.

[simoninithomas]

Hey there, I updated the doc: removed tennis illustration and added the link in ML-Agents-Overview.md#Training in Competitive Multi-Agent Environments with Self-Play