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

.vscode/settings.json

@@ -11,6 +11,8 @@
         "muks",
         "prefs",
         "unban",
-        "unredact"
+        "unifiedpush",
+        "unredact",
+        "webpush"
     ]
 }