xos-sample-gui-extension cleanup and update with new documentation

Change-Id: I6b70f5127ea631cfdd1f8a372a51c20f547e9c44
diff --git a/src/app/components/demo.html b/src/app/components/demo.html
index a85c5a9..dbf71ed 100644
--- a/src/app/components/demo.html
+++ b/src/app/components/demo.html
@@ -24,8 +24,9 @@
     <p>This page is loaded from an external container!</p>
   </div>
   <div class="col-xs-12">
-    From this extension you can use all the feature provided by the core, <br/>
-    for example you can toggle the side panel injecting custom content.
+    From this extension you can use all the features provided by the core. <br/>
+    For example, you can toggle the side panel by injecting custom content. <br/>
+    You can also create custom keyboard shortcuts. Try pressing "p" on your keyboard <br/>
     <br/>
     <br/>
     <a ng-click="vm.togglePanel()" class="btn btn-success">Open Side Panel</a>