Add CODE_OF_CONDUCT.md combining Contributor Covenant v1.4 and Rust CoC

[StaySafe020]

This PR adds a CODE_OF_CONDUCT.md file to the project, addressing issue #19.
some changes

• Defines welcoming and unacceptable behaviors tailored to our project.
• Adds a tiered enforcement approach for clarity and fairness.
• Blends the formal structure of Contributor Covenant with the Rust CoC’s collaborative tone.

[bansikah22]

@StaySafe020 if you done working you should assign at least 4 reviewers so that they can merge your work

[Blindspot22]

Suggested change

In the interest of fostering an open and welcoming environment, we as contributors, maintainers, and members of [async chat library], an async chat library built in Rust, pledge to make participation in our project and community a harassment-free experience for everyone, regardless of age, body size, disability, ethnicity, gender identity and expression, level of experience, nationality, personal appearance, race, religion, sexual identity and orientation, or other characteristics.

In the interest of fostering an open and welcoming environment, we as contributors, maintainers, and members of [async chat library](https://github.com/Rust-Cameroon/async-chat), an async chat library built in Rust, pledge to make participation in our project and community a harassment-free experience for everyone, regardless of age, body size, disability, ethnicity, gender identity and expression, level of experience, nationality, personal appearance, race, religion, sexual identity and orientation, or other characteristics.

[Blindspot22]

Suggested change

Instances of abusive, harassing, or unacceptable behavior may be reported to the project maintainers at [yemelechristian2@gmail.com],[abonghoderick@gmail.com] or via a private GitHub Issue/Discussion. All complaints will be reviewed and investigated promptly and fairly, with a response appropriate to the circumstances. Maintainers are obligated to maintain confidentiality regarding the reporter of any incident.

Instances of abusive, harassing, or unacceptable behavior may be reported to this [email](inforustcameroon@gmail.com) or via a private GitHub Issue/Discussion. All complaints will be reviewed and investigated promptly and fairly, with a response appropriate to the circumstances. Maintainers are obligated to maintain confidentiality regarding the reporter of any incident.

And abonghoderick is not a maintainer

[Christiantyemele]

why do i see this conflicts lines in your doc. please remove them @StaySafe020