input: Write a python function to sort a given list of strings using insertion sort.
  assert insertion_sort(['banana', 'apple', 'cherry'])==['apple', 'banana', 'cherry']
  assert insertion_sort(['dog', 'cat', 'elephant', 'bear'])==['bear', 'cat', 'dog', 'elephant']
  assert insertion_sort(['zebra', 'monkey', 'ape', 'giraffe'])==['ape', 'giraffe', 'monkey', 'zebra']
output: def insertion_sort(lst):
      for i in range(1, len(lst)):
          key = lst[i]
          j = i - 1
          while j >= 0 and key < lst[j]:
              lst[j + 1] = lst[j]
              j -= 1
          lst[j + 1] = key
      return lst