Clarified use of assets folder with admonition.

src/docs/asciidoc/jme3/beginner/hello_asset.adoc

@@ -129,6 +129,8 @@ MyGame/...
 
 This is just a suggested best practice, and it's what you get by default when creating a new Java project in the jMokeyEngine <<sdk#,SDK>>. You can create an `assets` directory and technically name the subdirectories whatever you like.
 
+IMPORTANT: When you build your project for distribution, there will be no `assets` directory. Instead, you will generate an `assets.jar` file, located in the `dist/lib` folder of your project that will contain the sub-folders of the `assets` directory and all the assets in those folders.
+
 
 === Loading Textures