update adapters to provide a verify function for custom hashing functions

[frankiebee]

For custom hashing function signatures to be verified if the hashing function for the program is a custom one we will now need the adapter to name the hashing algorithm and export a verify function that meets the spec.

// some adapter file
export const HASHING_ALGORITHM = 'sha256'
export function verify (sig): Promise<boolean> {}

the verify functions provided by adapters will be under entropy.sign.adapters[type].verify