FIXED:
- Fixed bug that would cause errors when players were near a class with walking mode enabled, but the class itself was not open.
- Really small leave optimization that will affect rare use-cases.

ADDED:
- Added menu syncing: when some change is made, all the opened menus for other players will adapt that change. This is currently in experimenting mode but will be polished in future updates.
- Added the first condition for lessons: the 'Minimum Time' condition will make sure your players won't abuse the lesson system. Only after a certain amount of seconds, the lesson may be ended (set to 0 to disable). Reloading the server still forcefully ends the lesson.
- Added small feature that will close all opened menus from this plugin when reloading (this would sometimes cause errors afterwards).

CHANGED:
- Teachers now have to be near the room spawn as well in order to start the lesson.