feat(hash): use common Sha interface for Sha1, Sha256 and Sha512

[v1rtl]

each SHA algorithm in std/hash has their own class but since all of them have the same set of functions it'd be smart to have a common interface that all these classes implement.

This PR adds a hash/types.ts file which exports Sha and Message types for convinience.

Example use case:

import type { Sha } from 'https://deno.land/std/hash/types.ts'

const createHash = (algo: string, key: string): Sha => {
  // ...
}

this will also ease adding std/node/crypto createHmac function in the future

[kt3k]

Sorry for not mentioning this in hash/README explicitly, but we are in the process of deprecating std/hash
ref: #1025

this will also ease adding std/node/crypto createHmac function in the future

This makes sense to me. Maybe we move these types somewhere in std/node?

[v1rtl]

oh alright then

I don't think it makes sense to have it in node cuz there's already Hash class

and also I was planning on using SHA from std/hash but if it's going to be replaced with crypto.subtle I probably should use it instead