Visibility of earlier cards in the history

[miselico]

When a bot is looking trough the history of the game, it might be useful to have that part the opponent hand which has been played later visible. The bot could, for example, use this to learn the opponent's strategy.

We could, for example, have:

    def get_move(self, state: PlayerGameState) -> Card:
        if state.leaders_turn():
            previous_state = state.get_previous()
            opponent_hand = previous_state.opponent.hand
            # at this point, the card of the last trick is back in the hand of the opponent, so we might as well make it visible