[patch] Export emojiAvatarForAddress from rainbowkit

Summary:
We want to export the emojiAvatarForAddress function from rainbowkit so we can "create our own ConnectButton".

With the address (via useAccount()), the emoji (via emojiAvatarForAddress), the AccountModal (via useAccountModal()), and (potentially) the ENS Avatar (via wagmi:useEnsAvatar()): we have everything we need.

Test Plan:
Able to log the avatar from SIWELoginForm:

Reviewers: ashoat, tomek

Reviewed By: ashoat

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D6548