input: Write a python function to find the length of the longest word in a list of words.
  assert longest_word_length(['apple', 'banana', 'cherry', 'date']) == 6
  assert longest_word_length(['a', 'ab', 'abc', 'abcd', 'abcde']) == 5
  assert longest_word_length(['hello', 'world', 'Python', 'programming']) == 11
output: def longest_word_length(words):
      return max(len(word) for word in words)