Push Notifications (#66)

Fixes #35.

Things to do:
- [x] Register with local distributor
- [x] Register with homeserver
- [x] Recieve messages
- [x] Show notifications
- [ ] Notifications page (could come later)

Reviewed-on: #66

pubspec.yaml

@@ -79,6 +79,10 @@ dependencies:
     app_links: 7.2.1
     file_selector: 1.1.0
     material_ui: 1.2.0
+    unifiedpush: 6.2.0
+    unifiedpush_storage_shared_preferences: 1.0.0
+    flutter_local_notifications: 22.3.0
+    flutter_local_notifications_linux: 8.0.1
 
 dev_dependencies:
     build_runner: 2.16.1
@@ -87,6 +91,8 @@ dev_dependencies:
     riverpod_lint: 3.1.9
     flutter_launcher_icons: 0.14.4
     json_serializable: 6.14.1
+    # Transitive dep but needed for commands
+    webcrypto: any
 
 flutter_launcher_icons:
     image_path: assets/icon.png