Initial pass at push notifications + some fixes to the session management (#91)

* Fix: test the session during resume to ensure it's valid

* Don't delete sessions for now

* Add notifee and request notif permissions on first login

* Set unread notifications badge on app icon

* Trigger a notifee card on new notifications

* Experimental: use react-native-background-fetch to check for notifications

* Add missing mocks

* Fix to resumeSession()

__mocks__/@notifee/react-native.ts

@@ -0,0 +1,6 @@
+export default {
+  requestPermission: jest.fn(),
+  onForegroundEvent: jest.fn(),
+  setBadgeCount: jest.fn(),
+  displayNotification: jest.fn(),
+}