add comment about vec2 operations in point_in_view (#2455)

Author: DragonMoffon

arcade/camera/camera_2d.py

@@ -482,6 +482,10 @@ def point_in_view(self, point: Point2) -> bool:
         Take a 2D point in the world, and return whether the point is inside the
         visible area of the camera.
         """
+        # This is unwrapped from standard Vec2 operations,
+        # The construction and garbage collection of the vectors would
+        # increase this method's cost by ~4x 
+        
         pos = self.position
         diff = point[0] - pos[0], point[1] - pos[1]