Triangle: Add note about barycentric coordinates in .containsPoint() docs.

docs/api/math/Triangle.html

@@ -79,7 +79,9 @@
 		<div>
 		[page:Vector3 point] - [page:Vector3] to check.<br /><br />
 
-		Returns true if the passed vector is within the triangle.
+		Returns true if the passed vector is within the triangle in
+		[link:https://en.wikipedia.org/wiki/Barycentric_coordinate_system barycentric coordinates]
+		(the vector is projected onto the plane of the triangle before checking containment).
 		</div>
 
 		<h3>[method:Triangle copy]( [page:Triangle triangle] )</h3>