New Timer Command
Arena commands can now be scheduled with /arena timer. The timer syntax supports recurring schedules with every, delayed starts with in and fixed times with at.

Examples:

- /arena timer every 24h in 10m reset fast
- /arena timer in 2h reset normal
- /arena timer every 1d at 12pm reset fast
- /arena timer every 48h reset slow
- /arena timer <arena> every 24h reset fast
- /arena timer list
- /arena timer remove <id>

Credit to @AquaNot for this PR

Minecraft Updates
- The plugin is now fully compatible on any version of Minecraft between 1.16 and 26.2
- Copper chest inventories are now supported

New ForceLoadWorlds config option
- Will forcefully try load worlds if they aren't loaded when PlatinumArenas is loaded
- Useful when an unknown plugin adds new worlds and PlatinumArenas happens to load before said plugin

Bug Fixes
- Fixed player skulls with no UUID or Texture (only a name) causing errors
- Fixed player skulls not writing persistent data to file
- Fixed issues with arenas loading in modern versions of Minecraft
- Fixed issues with suspicious sand and gravel
- NBT that fails to load will no longer make the arena fail to load