[native] Add boilerplate for deep links on iOS

Summary: The code was modified according to https://reactnative.dev/docs/linking?syntax=ios.

Test Plan: Create a page with a link pointing to https://web.comm.app/invite and check if clicking it opens the app.

Reviewers: bartek, kamil, ashoat

Reviewed By: bartek, ashoat

Subscribers: ashoat, atul

Differential Revision: https://phab.comm.dev/D7216