message: Add: ledger `chainId` open method documentation
diff: @@ -93,6 +93,17 @@ It will set first one as the default _(index `0`)_, while the rest will be avail
  You will be able to change them using the `setDefaultAddress()` instance method _(See: [Wallet Object](wallet-object.md) for details))_.
  +```js
  +walletArguments.chainId: Number = 1
  +```
  +
  +Sets the `id` of the network _(eg: `homestead`, `ropsten`, etc...)_ you want your account to be opened under _(changes the `derivationPath` of the opened addresses)_.
  +
  +It will also be used if you don't provide one when trying to sign a transaction.
  +
  +Defaults to `id` `1`: `homestead`.
  +
  +
  **Usage examples:**
  Open the ledger wallet using the default number of addresses:
  @@ -112,3 +123,12 @@ const wallet = await open({ addressCount: 100 });
  await wallet.setDefaultAddress(12); //true
  ```
  +
  +Open the ledger wallet using a different chain id
  +```js
  +import { open } from 'colony-wallet/ledger';
  +
  +const wallet = await open({ chainId: 3 }); // ropsten
  +
  +await wallet.derivationPath; // m/44'/1'/0'/0/0
  +```
  