fix: web notifications to show in foreground + duplicates prevented

Signed-off-by: Heikki Hellgren <heikki.hellgren@op.fi>

plugins/notifications/dev/index.tsx

@@ -20,9 +20,11 @@ import {
   notificationsPlugin,
   NotificationsSidebarItem,
 } from '../src';
+import { signalsPlugin } from '@backstage/plugin-signals';
 
 createDevApp()
   .registerPlugin(notificationsPlugin)
+  .registerPlugin(signalsPlugin)
   .addPage({
     element: (
       <NotificationsPage
@@ -32,5 +34,5 @@ createDevApp()
     ),
     path: '/notifications',
   })
-  .addSidebarItem(<NotificationsSidebarItem />)
+  .addSidebarItem(<NotificationsSidebarItem webNotificationsEnabled />)
   .render();