Added a note describing a code behind Vector2/3.direction_to

(cherry picked from commit fa0683ed307d08a1ebc89966bcecdf9350e3098b)

doc/classes/Vector2.xml

@@ -123,7 +123,7 @@
 			<argument index="0" name="b" type="Vector2">
 			</argument>
 			<description>
-				Returns the normalized vector pointing from this vector to [code]b[/code].
+				Returns the normalized vector pointing from this vector to [code]b[/code]. This is equivalent to using [code](b - a).normalized()[/code].
 			</description>
 		</method>
 		<method name="distance_squared_to">

doc/classes/Vector3.xml

@@ -91,7 +91,7 @@
 			<argument index="0" name="b" type="Vector3">
 			</argument>
 			<description>
-				Returns the normalized vector pointing from this vector to [code]b[/code].
+				Returns the normalized vector pointing from this vector to [code]b[/code]. This is equivalent to using [code](b - a).normalized()[/code].
 			</description>
 		</method>
 		<method name="distance_squared_to">