Clarify points in Line2D doc

(cherry picked from commit 3c9c541c590fb2765d20f2336303f1932dbff38e)

doc/classes/Line2D.xml

@@ -86,7 +86,7 @@
 			The style for the points between the start and the end.
 		</member>
 		<member name="points" type="PoolVector2Array" setter="set_points" getter="get_points" default="PoolVector2Array(  )">
-			The points that form the lines. The line is drawn between every point set in this array.
+			The points that form the lines. The line is drawn between every point set in this array. Points are interpreted as local vectors.
 		</member>
 		<member name="round_precision" type="int" setter="set_round_precision" getter="get_round_precision" default="8">
 			The smoothness of the rounded joints and caps. This is only used if a cap or joint is set as round.