Map selection and voting with advanced GUI, you can add as many maps as you want, with it's own pages system with it's own file mapvote.yml with it's own item etc.
Added two new commands
/gr addmap <map name> - Can only be used during arena setup
/gr addmaparena <arena> <map name> - Can only be used to add a map to an existing arena
Added voting closing time and messages and settings associated with voting
1.21 is supported (I haven't tried testing it but it should work)
%map% placeholder has been added to arena game info message