GridHelper example added

docs/api/extras/helpers/GridHelper.html

@@ -11,6 +11,18 @@
 
 		<div class="desc">todo</div>
 
+		<h2>Example</h2>
+
+		<code>
+				var size = 10;
+				var step = 1;
+				var gridHelper = new THREE.GridHelper(size, step);
+				
+				gridHelper.position = new THREE.Vector3(10,10,0);
+				gridHelper.rotation = new THREE.Euler(15,0,0);
+				
+				scene.add( gridHelper );
+		</code>
 
 		<h2>Constructor</h2>