input: Write a python function to rotate a given 2D array by 90 degrees clockwise.
  assert rotate90([[1, 2, 3], [4, 5, 6], [7, 8, 9]]) == [[7, 4, 1], [8, 5, 2], [9, 6, 3]]
  assert rotate90([[1, 2], [3, 4]]) == [[3, 1], [4, 2]]
  assert rotate90([[1]]) == [[1]]
output: def rotate90(matrix):
      return [list(row) for row in zip(*matrix[::-1])]