Prioritize active discord users for puppet accounts

[aaronpk]

When running with a limited number of puppets, I've found that random discord users get added to IRC and often times those users are not even active on the discord side. It would be great if the bridge could prioritize which users get puppet accounts so that active discord users appear better on the IRC side.

If it's too complicated to prioritize automatically, I'd be fine defining a list of discord users that get puppet account priority instead.