text: // Write a function "ticTacToe" which takes a two-dimensional array of size 3x3.
  // Each cell in the two dimensional array can be one of 'O', 'X', or null.
  // Return 'O' if O makes a winning row.
  // Return 'X' if X makes a winning row.
  // Return null if there is no winning row on the board.
  //
  // Examples:
  // > ticTacToe([
  //   ['O', 'O', 'O'],
  //   ['X', null, 'X'],
  //   [null, 'X', null]
  //   ])
  // 'O'
  // > ticTacToe([
  //   ['O', 'X', 'O'],
  //   ['O', 'X', null],
  //   [null, 'X', null]
  //   ])
  // 'X'
  // > ticTacToe([
  //   ['O', 'X', 'O'],
  //   ['O', 'O', null],
  //   [null, 'X', 'X']
  //   ])
  // null
  
  const emptyBoard = [
      [null, null, null],
      [null, null, null],
      [null, null, null]
  ]
  