Update class_curve2d.rst

Clarify that the position input to add_point is a position relative to the Curve2D's own position

classes/class_curve2d.rst

@@ -92,7 +92,7 @@ Method Descriptions
 
 - void **add_point** **(** :ref:`Vector2<class_Vector2>` position, :ref:`Vector2<class_Vector2>` in=Vector2(0, 0), :ref:`Vector2<class_Vector2>` out=Vector2(0, 0), :ref:`int<class_int>` at_position=-1 **)**
 
-Adds a point to a curve at ``position``, with control points ``in`` and ``out``.
+Adds a point to a curve at ``position`` relative to the Curve2D's position, with control points ``in`` and ``out``.
 
 If ``at_position`` is given, the point is inserted before the point number ``at_position``, moving that point (and every point after) after the inserted point. If ``at_position`` is not given, or is an illegal value (``at_position <0`` or ``at_position >= [method get_point_count]``), the point will be appended at the end of the point list.