Add Code of Conduct Document

[dylanpulver]

Summary:
This PR introduces a Code of Conduct document to the Safety CLI project. The document outlines the standards for behavior expected from all contributors and maintainers, promoting a welcoming and harassment-free environment.

Why this is important:
- Fosters Inclusivity: Establishes clear guidelines to ensure a welcoming and inclusive environment for all participants, regardless of background.
- Sets Behavioural Standards: Clearly defines acceptable and unacceptable behaviours, helping to prevent harassment, discrimination, and other negative actions.
- Guides Conflict Resolution: Provides a framework for addressing conflicts and resolving issues in a constructive manner.
- Encourages Professionalism: Reinforces the expectation of professional behavior in all project-related interactions, both online and offline.
- Supports Community Growth: By promoting a positive and respectful community, it helps attract and retain contributors who feel safe and valued.

By implementing this Code of Conduct, we aim to create a healthier, more productive, and more inclusive community for everyone involved in the Safety CLI project.

[davidlacho]

Some of this language is somewhat out-of-date, and the code of conduct from contributor-covenant.org has been updated since that version we're citing here.

I'd also recommend that we take some time brainstorming a better code of conduct that might reflect our values more closely, and that give more specific context to our workplace and standards 🌴🥥.

Since we don't have a Code of Conduct, I'll approve this but I would love for this to be a good discussion for us in the future.

Thanks for making this PR, @dylanpulver