Important commands:
Start game (spread players, lives to 3, etc.):
/function qwesome:life/start
Enable and disable rendering of current hearts for all players:
/function qwesome:life/global_display_enable
/function qwesome:life/global_display_disable
Enable and disable rendering of current hearts for yourself (non-op):
/trigger player_enable
/trigger player_disable
Set lives:
/team join (0-3) (player)