input: Write a function to append the first letter of each string to the end of the string.
  assert append_first_letter_end(['apple', 'banana', 'cherry']) == ['applea', 'bananab', 'cherryc']
  assert append_first_letter_end(['dog', 'cat', 'fish']) == ['dogd', 'catc', 'fishf']
  assert append_first_letter_end(['hello', 'world', 'python']) == ['helloh', 'worldw', 'pythonp']
output: def append_first_letter_end(words):
      return [word + word[0] for word in words]