Add Window_HUD to example manifest;

examples/init.lua

@@ -47,6 +47,7 @@ return {
   'Effects/Cubemap_Generate',
   'Effects/Cubemap_Texturing',
   'UI/Spectator_Camera',
+  'UI/Window_HUD',
   'Optimization/Instancing',
   'Debugging/FPS_Controls',
   'Debugging/Raw_Input',