adding addressByPrivateKey function

[0xPranjl]

added addressByPrivateKey

[pubkey]

I am not sure if we need this. Also this uses the ethers lib, but it could be done with plain functions that exist in this module already

const publicKey = EthCrypto.publicKeyByPrivateKey(myPrivateKey);
const address = EthCrypto.publicKey.toAddress(publicKey);