Fix bug where distance is not defined

extra.py

 from library import IDABot, Unit, UnitType, TypeData, Point2DI, PLAYER_SELF
 from typing import Optional
 
+Point2D.distance = lambda self, other: sqrt((self.x - other.x)**2 + (self.y - other.y)**2)
+
 
 def has_addon(bot: IDABot, candidate: Unit, addon_type: UnitType):
     """