[desktop/web] Expose callbacks needed for desktop notifications

Summary:
For macos notifs we need to expose two functionalities from the web app to the desktop app:

• setting the device_token that we will get from native macos api
• navigate to a thread after a notification is clicked

Test Plan: Tested with the rest of the stack, if the device token is set correctly and the app navigates to a thread.

Reviewers: tomek, inka, kamil

Reviewed By: kamil

Subscribers: ashoat, atul

Differential Revision: https://phab.comm.dev/D6891