Update CONTRIBUTING.md

Note on changing scenes.

Author: popcar2

CONTRIBUTING.md

@@ -13,7 +13,8 @@ One thing I will always welcome is more games! There are just a few notes I have
 * **Try to make your game as small as you can.** GodotOS is built in mind to run on the web, so any large files can greatly detract from its loading times and portability.
 As a rule of thumb, try to make your game under 1 megabyte. Consider compressing your assets, going for a pixel-art or minimalist style, using a sprite atlas, etc.
 * Don't use autoloads in your game since it would have to always be running for the entire application. If you **really** need an autoload, consider passing data through save files or adding a node in `/root/`.
-  Just make sure to delete it on window exit. 
+  Remember to delete it on window exit if you're doing this!
+* Avoid using functions that affect the entire scene such as `get_tree().change_scene_to_file()`. This will affect GodotOS as a whole, not just your game. Check the official games included for examples on how to safely change scenes only for the game window.
 * Make sure your scene and script names less generic. If you have a player and the game is called Super Bit Boy for example, call it `bit_boy_player.gd` instead of `player.gd`.
 
 That's it. Good luck!