input: Write a python function to find words containing a specific letter.
  assert find_words_containing_letter('Hello World', 'H') == ['Hello']
  assert find_words_containing_letter('apple banana cherry date', 'a') == ['apple', 'banana', 'cherry']
  assert find_words_containing_letter('python programming language', 'p') == ['python', 'programming']
output: def find_words_containing_letter(sentence, letter):
      return [word for word in sentence.split() if letter in word]