Write a function that removes all vowels from the input string. If the second parameter is passed, then remove these characters from the input string.
Input 1:
const inputString = "JavaScript is awesome";
removeLetters(inputString);
Output 1:
"JvScrpt s wsm"
Input 2:
removeLetters(inputString, "aw");
Output 2:
"JvScript is esome"