Add ability for opponents to extend time when player runs out of time

When players are having a good game but lose track of time, it can be frustrating to be surprised by the game ending suddenly. It would be nice if there was a way for opposing players to extend the game's time if they wish to keep it going.

Perhaps a popup with the text: "Do you wish to extend $PLAYER's time by $DURATION?" and buttons "YES" and "NO