Update javascript section in README

Signed-off-by: Julius Haertl <jus@bitgrid.net>

README.md

@@ -52,7 +52,8 @@ Nothing to prepare, just dig into the code.
 
 ### JavaScript
 
-Make sure you have installed the dependencies with ```make install-deps```. After that you can run ```make``` to build the javascript code once or run ```make watch``` to run in on every file change.
+When `'debug'=>true` is set in your config.php files will get loaded automatically. Otherwise you need to ensure that `public/app.js` is generated by running `make` or `make watch` to regenerate it on every change.
+Make sure you have installed the dependencies with ```make install-deps```.
 
 ### Running tests
 You can use the provided Makefile to run all tests by using: