[landing] add @farcaster/auth-kit dep

Summary:
We need this dep to sign in with farcaster.

Added the dep and ran yarn cleaninstall

Made @ashoat blocking since this diff adds a dependency

Test Plan: N/A; was able to successully utilze this package to sign into farcaster during the hackathon

Reviewers: ashoat, atul

Reviewed By: ashoat, atul

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D11426