Small change: explain the use of keys in JS documentation

[6r1d]

URL.

Text sections:

Let's assume that you have stringified public & private keys (more on that later)

const keyPair = crypto.KeyPair.fromJSON({
  public_key: 'ed0120e555d194e8822da35ac541ce9eec8b45058f4d294d9426ef97ba92698766f7d3',
  private_key: {
    digest_function: 'ed25519',
    payload:
      'de757bcb79f4c63e8fa0795edc26f86dfdba189b846e903d0b732bb644607720e555d194e8822da35ac541ce9eec8b45058f4d294d9426ef97ba92698766f7d3',
  },
})

Denis Kitaev requested the documentation update because it looks inconsistent for new users, specifically how keys were obtained for this code section.
I believe this key pair is taken from the Iroha JSON configuration file, but if it's more elaborate here, that'll greatly help the users.

[6r1d]

I could add another issue for this code, but I feel those topics are intertwined.

import { cryptoTypes } from '@iroha2/crypto-core'
import { Signer } from '@iroha2/client'
import { AccountId, DomainId } from '@iroha2/data-model'

// Key pair from previous step
declare const keyPair: cryptoTypes.KeyPair

const accountId = AccountId({
  // Account name
  name: 'alice',
  // The domain where this account is registered
  domain_id: DomainId({
    name: 'wonderland',
  }),
})

const signer = new Signer(accountId, keyPair)

Denis Kitaev also requested this information to be added to the JS SDK docs:

• Where does the alice account name come from?
• Is alice pre-set in the container peers?
• What about the wonderland domain?
• What about the key pair?

[kidys]

Yes it would be great if the documentation would explain step by step what to do... how to make requests from Node.js/JavaScript environment... Exactly step by step...