feat: add code of conduct

[naftalima]

Description

Adopting Contributor Covenant helps make your community’s values explicit, and signals your commitment to creating a welcoming and safe environment for everyone.

Motivation and Context

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [ ] My code follows the code style of this project.
• [ ] My change requires documentation updates.
• [ ] I have updated the documentation accordingly.
• [ ] My change requires dependencies updates.
• [ ] I have updated the dependencies accordingly.