input: Write a python function to add two arrays element-wise.
  assert add_arrays([1, 2, 3], [4, 5, 6]) == [5, 7, 9]
  assert add_arrays([10, 20], [30, 40]) == [40, 60]
  assert add_arrays([1, 1, 1], [1, 1, 1]) == [2, 2, 2]
output: def add_arrays(arr1, arr2):
      return [x + y for x, y in zip(arr1, arr2)]