Map notes

This update introduces a new map feature that has been requested multiple times in the past: the ability to add short notes as reminders.

This way, it will be easier to remember that medkit left in a chest or those large-caliber ammo stashed in a locker, without wandering too much trying to recall whether you turned right or left. :)

I hope this addition will be appreciated and make the lives of the volunteers a little bit easier as they roam the facility's corridors.