input: Write a python function to insert elements into a list at a given index.
  assert insert_list([1, 2, 3, 4], 2, [7, 8]) == [1, 2, 7, 8, 3, 4]
  assert insert_list(['a', 'b', 'c'], 1, ['x', 'y']) == ['a', 'x', 'y', 'b', 'c']
  assert insert_list([10, 20, 30], 0, [5, 15]) == [5, 15, 10, 20, 30]
output: def insert_list(lst, index, elements):
      return lst[:index] + elements + lst[index:]