input: Write a python function to add two matrices element-wise.
  assert add_matrices([[1, 2], [3, 4]], [[5, 6], [7, 8]]) == [[6, 8], [10, 12]]
  assert add_matrices([[1, 0], [0, 1]], [[0, 1], [1, 0]]) == [[1, 1], [1, 1]]
  assert add_matrices([[2, 2], [2, 2]], [[3, 3], [3, 3]]) == [[5, 5], [5, 5]]
output: def add_matrices(matrix1, matrix2):
      result = []
      for i in range(len(matrix1)):
          row = []
          for j in range(len(matrix1[0])):
              row.append(matrix1[i][j] + matrix2[i][j])
          result.append(row)
      return result