Mention CollisionPolygon2D.polygon is local to the given CollisionPolygon2D

(cherry picked from commit f5409dc132ae81c2819f30882a88fd3205fc046f)

doc/classes/CollisionPolygon2D.xml

@@ -25,6 +25,7 @@
 		</member>
 		<member name="polygon" type="PackedVector2Array" setter="set_polygon" getter="get_polygon" default="PackedVector2Array()">
 			The polygon's list of vertices. Each point will be connected to the next, and the final point will be connected to the first.
+			[b]Note:[/b] The returned vertices are in the local coordinate space of the given [CollisionPolygon2D].
 			[b]Warning:[/b] The returned value is a clone of the [PackedVector2Array], not a reference.
 		</member>
 	</members>