[testing] add details on cairo test runner cheatcodes about book

[od-hunter]

Hi @glihm , I will go through the testing.cairo file to study and test the test functions. I will then create a new section explaining how each of them work with code examples.
This is my first time contributing to this ecosystem please assign me thank you.

[od-hunter]

Hello @glihm , I’m ready to be assigned by you so I can start work.

[od-hunter]

Can I be assigned this project please?

[vicjuma]

I can handle this. Can it be assigned to me kindly

[glihm]

Can I be assigned this project please?

As you commented first will assign to you if you feel confident about the work to be done here. Any idea to where you'll start?

[od-hunter]

Thank you🙏🏾

[od-hunter]

Hello @glihm kindly review please

[od-hunter]

@glihm kindly review please