Function flip

flip(board: Board, playerId: string, row: number, column: number): Promise<string>
Tries to flip over a card on the board, following the rules in the ps4 handout. If another player controls the card, then this operation blocks until the flip either becomes possible or fails.

Returns
the state of the board after the flip, in the format described in the ps4 handout

Throws
an error (rejecting the promise) if the flip operation fails as described in the ps4 handout.
Parameters
- board: Board
  
  a Memory Scramble board
- playerId: string
  
  ID of player making the flip; must be a nonempty string of alphanumeric or underscore characters
- row: number
  
  row number of card to flip; must be an integer in [0, height of board), indexed from the top of the board
- column: number
  
  column number of card to flip; must be an integer in [0, width of board), indexed from the left of the board
Returns Promise<string>