Add raytracing_sandbox_workers to examples index

examples/index.html

@@ -475,7 +475,8 @@
 				"canvas_sandbox"
 			],
 			"raytracing": [
-				"raytracing_sandbox"
+				"raytracing_sandbox",
+				"raytracing_sandbox_workers"
 			],
 			"software": [
 				"software_geometry_earth",