Explain the 2D contour

state the format of a contour as a arument

docs/api/en/extras/ShapeUtils.html

@@ -22,7 +22,7 @@
 
 		<h3>[method:Number area]( contour )</h3>
 		<p>
-		contour -- 2D polygon.<br /><br />
+		contour -- 2D polygon. An array of THREE.Vector2(), according to the <a href="https://github.com/mrdoob/three.js/blob/master/src/extras/ShapeUtils.js#L18">definition</a> of the method.<br /><br />
 
 		Calculate area of a ( 2D ) contour polygon.<br /><br />