Add a Leaderboard

Idea moved from Tournament Wish List (TOP Tournament):

Automated Leaderboard. Game results are used to calculate leaderboard points. This leaderboard is reset at the beginning of each month. Winners get 5 pts, and all other places get 2 pts. if a player leaves for any reason other than quitting, they get the points their seat finished at with a sub (they get 0 if they quit and possibly banned for a period of time). If a player subs, they also get the points for that seat plus 1 point for subbing (maximum 5 points per round). if a player played in a round and subbed for someone else, they get the larger of the points earned from either game, plus 1 point, but maximum 5 points for any round. The top 16 on our leaderboard play in our end-of-month championship, which has different point rules that don't count towards the leaderboard but just for the championship game. Our end-of-year championship also follows a format like end-of-month.