docs(ngOpen): improve example, correct browser compat note

Firefox supports details since version 49

Author: Narretz

src/ng/directive/attrs.js

@@ -317,15 +317,20 @@
  *
  * ## A note about browser compatibility
  *
- * Edge, Firefox, and Internet Explorer do not support the `details` element, it is
+ * Internet Explorer and Edge do not support the `details` element, it is
  * recommended to use {@link ng.ngShow} and {@link ng.ngHide} instead.
  *
  * @example
      <example name="ng-open">
        <file name="index.html">
-         <label>Check me check multiple: <input type="checkbox" ng-model="open"></label><br/>
+         <label>Toggle details: <input type="checkbox" ng-model="open"></label><br/>
          <details id="details" ng-open="open">
-            <summary>Show/Hide me</summary>
+            <summary>List</summary>
+            <ul>
+              <li>Apple</li>
+              <li>Orange</li>
+              <li>Durian</li>
+            </ul>
          </details>
        </file>
        <file name="protractor.js" type="protractor">