Write a function `popularLetters(string)` that takes a string as an argument and returns an array of all of the characters that appear five or more times in the string. Examples: ***********************************************************************/ console.log(popularLetters('apple')); // [] console.log(popularLetters('bananas in pajamas')); // [ 'a' ] console.log(popularLetters('Yes, we have no bananas, we have no bananas today!')); // [ 'e', ' ', 'a', 'n' ]