Add an API to show a count in the document title

js/forum/src/components/DiscussionPage.js

@@ -184,6 +184,7 @@ export default class DiscussionPage extends mixin(Component, evented) {
     this.discussion = discussion;
 
     app.setTitle(discussion.title());
+    app.setTitleCount(0);
 
     // When the API responds with a discussion, it will also include a number of
     // posts. Some of these posts are included because they are on the first

js/forum/src/components/IndexPage.js

@@ -96,6 +96,7 @@ export default class IndexPage extends Component {
     };
 
     app.setTitle('');
+    app.setTitleCount(0);
 
     // Work out the difference between the height of this hero and that of the
     // previous hero. Maintain the same scroll position relative to the bottom