input: Write a function to add two arrays element-wise.
  assert add_arrays([2, 3, 4], [5, 6, 7]) == [7, 9, 11]
  assert add_arrays([1, 2, 3], [4, 5, 6]) == [5, 7, 9]
  assert add_arrays([0, 0, 0], [1, 2, 3]) == [1, 2, 3]
output: def add_arrays(arr1, arr2):
      return [x + y for x, y in zip(arr1, arr2)]