Added save info to admonition.

src/docs/asciidoc/jme3/external/blender.adoc

@@ -228,6 +228,7 @@ You can also use the SDK to invert the channel:
 
 .  In the SDK, btn:[RMB] select the image and choose "`Edit Texture`".
 .  In the window header, press the btn:[Filters] button and choose `menu:Invert[Green]`.
+.  When satisfied, save the change in the same format as the original image using `menu:File[Save]`.  
 ====
 
 === LightMap baking