A palindrome is a series of letters or numbers that reads equivocally backwards.
Write a recursive function that determines whether a given string is a palindrome or not.
isPalindrome("Maneuquenam") ➞ true
isPalindrome("This phrase, surely, is not a palindrome!") ➞ false
isPalindrome("Eva, can I see bees in a cave?") ➞ true