Added a feature where your inventory is being cleared when you join a level and is being filled with level items (leave and returnToCP). The inventory will be restored once you leave/finish a level.
Added customization for the menu data (menu title, close name).
Fixed a bug where the items in the level menu weren't the custom set level end blocks, but the default ones (wool).
Fixed a bug where the item validation wasn't ready for 1.13, so the plugin would shut down when it detected an item of 1.13.
Fixed the /checkpoints reloaded command where it didn't reload properly.
Big thanks to @Ciro998 for all his help regarding this update.