Various spectate mode fixes. Various fixes on how duel players are protected from others. Fixed an issue when in case of inventory-saving, if player left he didn't receive his inventory and only did so if he died after.

Fixes: added /duels stopspectate command in default spectator command whitelist. you could add it yourself in the config btw. Fixed a bug, where if a player won, spectators could hurt him in the 10 second item pickup period. Fixed an error in console.

Added new language.yml options

Fixed players getting stuck in duel arena when they left the game. (the teleportation handler was glitchy)

Added 1.21.8 support

Fixed incompatibility issues on sunlight