Add mods_order.txt note to upgrade doc, closes #347

Author: burner1024

docs/update.md

@@ -1,10 +1,12 @@
 ## Update
 
-Make sure to **backup your saves** or better yet, the entire game directory **before** updating.
+Make sure to **backup your saves** or better yet, the entire game directory before updating.
 
 - You can update from an older RPU version.
 - You can install RPU on top of RP 2.3.3 to make use of the fixes.
 
 In both cases, you won't see some of the fixes on already visited maps. Other than that, savegames should be compatible, but **no guarantees**.
 
 If you made any changes to `ddraw.ini`, these changes will be lost when you overwrite that file. If you want to preserve them, make a backup copy and then transfer the settings manually to the new `ddraw.ini`.
+
+The same goes for `mods\mods_orders.txt`. If you altered that file, you'll have to transfer the changes manually. You can find the old file in `backup/mods_order.txt` inside game directory.