Merge pull request #1051 from multiversx/TOOL-444-add-relayed-v-3-documentation

Add relayed v3 documetation

Author: danielailie

docs/sdk-and-tools/sdk-js/sdk-js-cookbook-v13.md

@@ -107,6 +107,48 @@ const tx = new Transaction({
 tx.nonce = 42n;
 ```
 
+### Preparing a relayed transaction
+
+We are currently on the third iteration of relayed transactions. V1 and V2 are soon to be deactivated so we'll focus on V3.
+For V3, two new fields have been added on transactions: `relayer` and `relayerSignature`.
+Before the sender signs the transaction, the relayer needs to be set. After the sender has signed the transaction, the relayer can also sign the transaction and broadcast it.
+Keep in mind that, for relayed V3 transactions we need an extra 50_000 gas. Let's see how we can create a relayed transaction:
+
+```js
+import { Transaction } from "@multiversx/sdk-core";
+
+const grace = await loadTestWallet("grace");
+
+# alice will be our relayer, that means she is paying the gas for the transaction
+const alice = await loadTestWallet("alice");
+const transactionComputer = new TransactionComputer();
+
+# fetch the sender nonce of the network
+const nonce = (await apiProvider.getAccount(grace.getAddress())).nonce;
+# create the transaction
+const transaction = new Transaction({
+    receiver: grace.getAddress().bech32(),
+    sender: grace.getAddress().bech32(),
+    gasPrice: BigInt(1000000000),
+    gasLimit: BigInt(150000),
+    chainID: "D",
+    nonce: BigInt(nonce),
+    relayer: alice.getAddress(),
+    value: BigInt(1),
+});
+
+# sender signs the transaction
+transaction.signature = await grace.signer.sign(transactionComputer.computeBytesForSigning(transaction));
+const buffer = transactionComputer.computeBytesForSigning(transaction);
+
+# relayer signs the transaction
+const signature = await alice.signer.sign(Buffer.from(buffer));
+transaction.relayerSignature = signature;
+
+# broadcast the transaction
+await proxyProvider.sendTransaction(transaction);
+```
+
 ### Signing a transaction
 
 :::important