message: docs: fix wallet generateNewAccount documentation
diff: @@ -120,12 +120,16 @@ interface Wallet {
  Accounts allow users to use separate Stacks addresses from within the same wallet. Each account has it's own Stacks address and balance. When a user logs into an app, they choose a specific account.
  -When using `generateNewAccount`, the new account is created with next index, based on the existing accounts in a wallet. For example, if a wallet has 5 accounts, calling `generateNewAccount` will make the sixth account.
  +When using `generateNewAccount`, the new account is created with next index, based on the existing accounts in a wallet. For example, if a wallet has 5 accounts, calling `generateNewAccount` will make the sixth account. The `generateNewAccount` treats as the input wallet as immutable. It returns a new wallet object with all available accounts (based on the input wallet object and the additional generated account).
  ```typescript
  -import { generateNewAccount } from '@stacks/wallet-sdk';
  +import { generateWallet, generateNewAccount } from '@stacks/wallet-sdk';
  -const account = generateNewAccount(wallet);
  +let wallet = await generateWallet({
  + secretKey,
  + password,
  +});
  +wallet = generateNewAccount(wallet); // adds a new account to an existing wallet object, immutable, NOT in-place
  ```
  An `Account` is a JavaScript object with these properties:
  