input: Write a python function to pad a list to a given length with the last element in the list.
  assert pad_list_right([1, 2, 3], 5) == [1, 2, 3, 3, 3]
  assert pad_list_right([4, 5, 6], 8) == [4, 5, 6, 6, 6, 6, 6, 6]
  assert pad_list_right([7, 8, 9], 4) == [7, 8, 9, 9]
  assert pad_list_right([10, 11], 2) == [10, 11]
output: def pad_list_right(lst, length):
      if len(lst) == 0:
          return lst
      while len(lst) < length:
          lst.append(lst[-1])
      return lst