[native] implement UI for TagUnfollowedFarcasterChannel screen

Summary:
This diff introduces the UI for the TagUnfollowedFarcasterChannel screen. For the UI, I tried to use our invite link screens as inspiration for this UI

Depends on D11855

Test Plan:
Please see the demo video below

Reviewers: inka

Reviewed By: inka

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D11857