Add Scene.mouse_drag_point

Author: eulertour

manim/scene/scene.py

@@ -1006,5 +1006,6 @@ def on_key_release(self, symbol, modifiers):
         pass
 
     def on_mouse_drag(self, point, d_point, buttons, modifiers):
+        self.mouse_drag_point.move_to(point)
         self.camera.increment_theta(-d_point[0])
         self.camera.increment_phi(d_point[1])