Document creating groups in ballchasing

[xhalo32]

The README should have information on how the division groups should be created, i.e. which settings to pick:

Player identification:

• By platform ID (Steam ID, PSN ID, XBox ID, etc.)
• Player name

Team identification:

• A Teams has the same distinct set of players
• A Team players may change from game to game (subs, rotations)

Supposedly the best configuration is By platform ID & players may change.