input: Write a python function to generate all combinations with replacement of a given list of characters of length 2 using itertools.
  assert generate_combinations_with_replacement(['a', 'e', 'i', 'o', 'u']) == ['aa', 'ae', 'ai', 'ao', 'au', 'ee', 'ei', 'eo', 'eu', 'ii', 'io', 'iu', 'oo', 'ou', 'uu']
  assert generate_combinations_with_replacement(['x', 'y', 'z']) == ['xx', 'xy', 'xz', 'yy', 'yz', 'zz']
  assert generate_combinations_with_replacement(['p', 'q']) == ['pp', 'pq', 'qq']
output: def generate_combinations_with_replacement(char_list):
      import itertools
      return [''.join(comb) for comb in itertools.combinations_with_replacement(char_list, 2)]