Add full support for eip-3085 wallet_addEthereumChain

[iainnash]

Currently, viem does not allow passing in the iconUrls field to the wallet_addEthereumChain method call.

interface AddEthereumChainParameter {
  chainId: string;
  blockExplorerUrls?: string[];
  chainName?: string;
  iconUrls?: string[];
  nativeCurrency?: {
    name: string;
    symbol: string;
    decimals: number;
  };
  rpcUrls?: string[];
}

However, all other fields are present.

https://eips.ethereum.org/EIPS/eip-3085

This will likely require:

1. Updating chain type with an optional iconUrls string array
2. Adding the chain iconUrls to the wagmi/references/chains repo