Chore: Add a CODE_OF_CONDUCT.md file

[fred-maina]

Description

A healthy open-source community requires clear guidelines for interaction. A CODE_OF_CONDUCT.md file establishes these expectations and provides a process for reporting and handling violations. The existing CONTRIBUTING.md is good but does not serve this purpose.

Acceptance Criteria

1. Add a CODE_OF_CONDUCT.md file to the root of the repository.
2. Use a standard template, such as the Contributor Covenant.
3. Update the CODE_OF_CONDUCT.md file to specify an email address for reporting issues.
4. Link to this new file from the README.md and CONTRIBUTING.md files.