Refactor dashboard issues

app/assets/javascripts/dispatcher.js

@@ -199,6 +199,8 @@ import Activities from './activities';
           new Sidebar();
           break;
         case 'dashboard:issues':
+          import('./pages/dashboard/issues').then(callDefault).catch(fail);
+          break;
         case 'dashboard:merge_requests':
           projectSelect();
           initLegacyFilters();

app/assets/javascripts/pages/dashboard/issues/index.js

+import projectSelect from '~/project_select';
+import initLegacyFilters from '~/init_legacy_filters';
+
+export default () => {
+  projectSelect();
+  initLegacyFilters();
+}