update readme

README.md

@@ -63,8 +63,10 @@ Don't forget to import your styles in your `app.scss` **after** importing ember
 - `expanded` - defaults to `false` - this toggles the expansion panel between expanded and collapsed modes.
 - `onExpandedChange` - an action that is sent when a the panel is expanded or collapsed. You get as an argument a boolean with the current state of `expanded`
 
-This component yields a hash that contains the `collapsed` and `expanded` components.
-It also yields a `collapse` action you can use to collapse the panel (e.g use it with paper-button's onClick).
+This component yields a hash that contains:
+- `collapsed` and `expanded` components
+- a `collapse` action you can use to collapse the panel (e.g use it with paper-button's onClick)
+- an `isExpanded` boolean that tells you the current state of the panel
 
 ### `{{#panel.collapsed}}`