Basic working game (P1)

[StephenDriffill]

• [x] useReducer for board state
• [x] state for current player (X or O) - assume X makes first move
• [x] onClick handler to update board and switch player
• [x] remove handler / block state update if square is already used
• [x] check if player has won after each move e.g. hasPlayerWon - prevent more moves, display the winner and prompt to reset
• [x] handler to reset the board
• [x] Add unit tests for the helper functions (move and getWinner)