resourse https://gist.github.com/epoch/9b89da6bdc81fd91cf18f4c102844565
Write a method switchUp
that takes a string as an argument and returns the string with the case for each letter switched e.g. lowercase letter must become uppercase and vice versa.
switchUp("Switch caSe FoR eVery letter") // => "sWITCH CAsE fOr EvERY LETTER"