feat: login a user docs

[Ismail-butt]

Feat: login a user docs

Explain changes

I added login a user docs in this changing :)

Comments

I followed your youtube tutorial of Building a REST API and in the turorial you said, if you want to add any changings in the docs.You can do it and can send me the pull request. That's why after I completed your tutorial with side be side coding. I added create a user docs and wanted to make a pull request so you can also add it. I will also try to add docs to other endpoint in the future. Thanks for the beautifull tutorial!