Add CODE_OF_CONDUCT.md file

[Maryam0330]

I would like to add a CODE_OF_CONDUCT.md file to the repository to establish clear guidelines for acceptable behavior in the project. This will help foster an inclusive and positive environment for contributors, ensuring a respectful and collaborative atmosphere.

[Maryam0330]

@Devasy23 Please assign me this task under gssoc-ext level3 labels.