added Extra examples header

Seems it made sense to add the Extra Examples after the Code Example, but maybe that needs rethinking?

docs/api/lights/SpotLight.html

@@ -50,6 +50,7 @@
 		scene.add( spotLight );
 		</code>
 
+		<h2>Extra Examples</h2>
 		<div>
 		[example:webgl_materials_bumpmap materials / bumpmap]<br/>
 		[example:webgl_shading_physical shading / physical]<br/>