Move Codewars content from CYF Docs into Guides

**Which module(s) and week(s) does this change affect?**
Module(s): Guides
Week(s): N/A

**What is the work that needs to be done?**
I'd love some help to move the following pages from CYF Docs to our Curriculum.
- [Codewars](https://docs.codeyourfuture.io/leaders/running-the-course/codewars)
- [Codewards advice for CYFers](https://docs.codeyourfuture.io/leaders/running-the-course/codewars/codewars-advice-from-cyfers)
- [Codewards advice for mentors](https://docs.codeyourfuture.io/leaders/running-the-course/codewars/codewars-advice-from-mentors)

**Why is this work important to do?**
It's important so we can have all our main guides and supportive tasks for our participants and trainees in one location: the curriculum

**Additional context**

**Who might need to know about this change?**
@SallyMcGrath @kfklein15 - I need to know so I can archive the CYF Docs page when done