Adds a Marker2D attribute for Godot to be used in C#. In order to avoid cluttering up the scene tree with marker 2D nodes. A Vector 2 can be used instead. think of it as an offset marker
-Undo and Redo is unsupported
-Vector2 does not rotate with parent
Tag Any Vector2 field with [Marker2D] and when the node is selected a dot will appear in the viewport marking the location of that point in local coords from its parent. which can then be moved around. Tag a Vector2 with [Marker2D] to visualize where the point is in the scene and move it around the viewport. While the Node2D is Selected. The script must be marked as [Tool]
*might work with older versions of Godot but it is untested