Add signer for ledger live app

[michalsmiarowski]

Refs: threshold-network/token-dashboard#649

In the T dashboard repo we've created an ethereum signer for Ledger Live App (ref threshold-network/token-dashboard#655). We've decided to move it here.

The LedgerLiveAppEthereumSigner extends the Signer class from ethers. It implements all the needed methods, like getAddress, signMessage, signTransaction and connect. Additionaly I've added sendTransaction method that will be mainly used to communicate with contracts. All the methods use ledgergq/wallet-api-client under the hood.

Constructor

The Signer class has provider property tha we have to define in the constructor - that's why this is the argument needed to create an instance of our ledger live app ehtereum signer. Besides that we will also have _walletApiClient, _windowMessageTransport and _account properties in our class. The first two can be also passed through a constructor, but if they not they will be initialized automatically using our methods in src/lib/utils/ledger/wallet-api.ts. This is also the reason why I've decided to create a separate ledger folder in utils. (EDIT: I've actually moved everything to one ledger.ts file. See #743 (comment)).

Account

As i mentioned earlier, we also have _account property which will store an Account object (from @ledgerhw/wallet-api-client). This will be helpful whenn doing a transaction, because for that we will have to use account id, so storing only the address would not work.

The _account is managed trough getter and setter, so the user can request an account with either wallet-api-client or wallet-api-client-react and use setAccount setter to store it in our signer. The account MUST be set before doing transaction or signing a message. If it's not set, then the proper error will be thrown.

We can also get only the address through the getAddress method (required from Signer abstract class) and getAccountId, which is not really used anywhere, but might be helpful in some cases.

I've also created a requestAccount method if we would want to trigger the request account, but it will also not be used in our dApp, since we will be requesting an account through a hook from wallet-api-client-react and just setting the account with setAccount. I've decided to keep it there anyway, as it might be helpful for someone, who decides to use it in his app.

Sending transaction

Sending transaction uses wallet-api under the hood. An example ethereum transaction object, that we will be using with that library, can look like this:

const ethereumTransaction = {
  family: "ethereum",
  amount: new BigNumber(100000000000000),
  recipient: "0xRecipientAddress",
  nonce: 2,
  data: Buffer.from("SomeDataInHex", "hex"),
  gasPrice: new BigNumber(20000000000),
  gasLimit: new BigNumber(21000),
};

It is worth noticing that calling a contract method requires to:

1. Pass 0 as the amount,
2. Pass contract address as the recipient
3. Pass the hex data related to calling that method
4. Set the family to ethereum

The rest of the things are optional. It is also worht noticing that the lib uses BigNumber from bignumber.js library.

Connecting and disconnecting the transport

When doing any operation (like sending transaction or requesting an account) with wallet-api we have to connect the _windowMessageTransport just before doing that, and disconnect it just after to avoid some unexpected issues. It is as simple as calling this._walletMessageTransport.connect() and this._walletMessageTransport.disconnect() methods.

[michalsmiarowski]

Checked it out locally with the dApp and all works good (but had to update the ethers lib to the same version that is used in tbtc-v2.ts). Changing the status to Ready for review.