input: Write a python function to count occurrences of a specific character in a string.
  assert characterCounter("Hello! What is your name?", 'o') == 2
  assert characterCounter("Python programming is fun!", 'g') == 2
  assert characterCounter("This is a test string.", 't') == 4
output: def characterCounter(s: str, char: str) -> int:
      return s.count(char)