Add CONTRIBUTING.md and CODE_OF_CONDUCT.md files

[RaginiSharma01]

No description provided.

[RaginiSharma01]

I have added the contributing.d and code_of_conduct.md

[krzysdz]

The links should be updated like @ShubhamOulkar did in #6601 and point to files from expressjs/.github repository (see #6593 (comment)). Additionally, the link to the Code of Conduct is given at the bottom of README and that's where it should be changed (it's a collapsed reference link):

express/Readme.md

Line 272 in 98c85eb

[Code of Conduct]: https://github.com/expressjs/express/blob/master/Code-Of-Conduct.md

[RaginiSharma01]

i have made changes . and added the code of conduct

[bjohansebas]

Please keep the PR focused, this change is unnecessary

[bjohansebas]

It would be better if you created a new PR, since this change could block the goal of the current one, which is to bring that file back.

[bjohansebas]

The content of this file should say something like "The code of conduct is located in https://github.com/expressjs/.github/blob/HEAD/CODE_OF_CONDUCT.md" rather than bringing back the full content, since we don’t want to maintain two versions in different places.