Add new provider support for seif wallet

[dot-haechi]

We would like to support the connection of Seif Wallet's provider in Rainbowkit.

Please refer to the following link for an introduction to Seif Wallet:
Introduction Seif Wallet

Chrome store link:
Seif Wallet Chrome Store

A custom wallet can be implemented as shown below:
Seif Integration Sample

Could you make it possible to import Seif Wallet in Rainbowkit as shown below?

import {
  seifWallet
} from "@rainbow-me/rainbowkit/wallets";

[dot-haechi]

#2028
I open pull request for this.