input: Write a python function to replace vowels in a given string with an asterisk (*).
  assert replaceVowels("Hello World") == "H*ll* W*rld"
  assert replaceVowels("Programming is fun") == "Pr*gr*mm*ng *s f*n"
  assert replaceVowels("AEIOU") == "*****"
output: def replaceVowels(s):
      vowels = "AEIOUaeiou"
      return ''.join(['*' if char in vowels else char for char in s])