message: updated readme to reflect XpringClient object, added more detailed notes
diff: @@ -138,7 +138,7 @@ A `XpringClient` can check the balance of an account on the XRP Ledger.
  const { XpringClient } = require("xpring-js");
  const remoteURL = "grpc.xpring.tech:80";
  -const xpringClient = XpringClient.xpringClientWithEndpoint(remoteURL);
  +const xpringClient = new XpringClient(remoteURL);
  const address = "X7u4MQVhU2YxS4P9fWzQjnNuDRUkP3GM6kiVjTjcQgUU3Jr";
  @@ -164,11 +164,13 @@ These states are determined by the `TransactionStatus` enum.
  const { XpringClient } = require("xpring-js");
  const remoteURL = "grpc.xpring.tech:80";
  -const xpringClient = XpringClient.xpringClientWithEndpoint(remoteURL);
  +const xpringClient = new XpringClient(remoteURL);
  -const transactionHash = "2CBBD2523478848DA256F8EBFCBD490DD6048A4A5094BF8E3034F57EA6AA0522";
  +const transactionHash = "9FC7D277C1C8ED9CE133CC17AEA9978E71FC644CE6F5F0C8E26F1C635D97AF4A";
  const transactionStatus = xpringClient.getTransactionStatus(transactionHash); // TransactionStatus.Succeeded
  ```
  +**Note:** The example transactionHash may lead to a "Transaction not found." error because the TestNet is regularly reset, or the accessed node may only maintain one
  +month of history. Recent transaction hashes can be found in the XRP Ledger Explorer: https://livenet.xrpl.org/
  #### Sending XRP
  @@ -180,19 +182,22 @@ A `XpringClient` can send XRP to other accounts on the XRP Ledger.
  const { Wallet, XRPAmount, XpringClient } = require("xpring-js");
  const remoteURL = "grpc.xpring.tech:80";
  -const xpringClient = XpringClient.xpringClientWithEndpoint(remoteURL);
  +const xpringClient = new XpringClient(remoteURL);
  // Amount of XRP to send
  -const amount = BigInt("10")
  +const amount = BigInt("10");
  // Destination address.
  const destinationAddress = "X7u4MQVhU2YxS4P9fWzQjnNuDRUkP3GM6kiVjTjcQgUU3Jr";
  // Wallet which will send XRP
  -const senderWallet = Wallet.generateRandomWallet();
  +const generationResult = Wallet.generateRandomWallet();
  +const senderWallet = generationResult.wallet;
  const transactionHash = await xpringClient.send(amount, destinationAddress, senderWallet);
  ```
  +**Note:** The above example will yield an "Account not found." error because
  +the randomly generated wallet contains no XRP.
  ### Utilities
  #### Address validation
  