Add fn verifyMessage

[dawsbot]

Code example: https://runkit.com/dawsonbotsford/etherssignmessage
This will involve reverse-engineering how ethers does it
Ethers documentation: https://docs.ethers.io/v5/api/utils/signing-key/#utils-verifyMessage

const { utils } = ethers

const claimedMessage = '';
const signedMessage = '';
utils.verifyMessage( claimedMessage, signedMessage )