Remove empty line; add a tiny comment

demo/app/src/main/java/org/pf4j/demo/Boot.java

 
             protected ExtensionFinder createExtensionFinder() {
                 DefaultExtensionFinder extensionFinder = (DefaultExtensionFinder) super.createExtensionFinder();
-                extensionFinder.addServiceProviderExtensionFinder();
+                extensionFinder.addServiceProviderExtensionFinder(); // to activate "HowdyGreeting" extension
 
                 return extensionFinder;
             }
 
         };
 
-
         // load the plugins
         pluginManager.loadPlugins();