feat: add ccip read example (#228)

* feat: add ccip read example

packages/linea-ccip-gateway/README.md

@@ -24,3 +24,101 @@ pnpm i
 pnpm compile
 pnpm test
 ```
+
+## Example of how to use CCIP-Read using EtherJs
+
+This example demonstrates how to use CCIP-Read using EtherJs to call a contract that implements the protocol.
+
+### Interacting with the `TestL1` Contract Using CCIP-Read
+
+To interact with the `TestL1` contract using the CCIP-Read protocol, follow these steps:
+
+#### Prerequisites
+
+Before running the script, ensure that you have the necessary environment variables set up in your `.env` file:
+
+- **`INFURA_API_KEY`**: Your Infura project ID, which allows you to connect to the Ethereum network via Infura.
+
+#### Adding the Script
+
+Create a new script file in your project directory at `scripts/testL1.ts` and add the following code:
+
+```js
+import { ethers } from "ethers";
+import "dotenv/config";
+
+// Define the ABI for the getLatest function
+const getLatestABI = [
+  {
+    inputs: [],
+    name: "getLatest",
+    outputs: [
+      {
+        internalType: "uint256",
+        name: "",
+        type: "uint256",
+      },
+    ],
+    stateMutability: "view",
+    type: "function",
+  },
+];
+
+async function main() {
+  /* 
+  Address of the deployed TestL1 contract on the Sepolia testnet.
+  You can view the contract on Etherscan using the following link:
+  https://sepolia.etherscan.io/address/0xb12038acce44e39dd5b2f59f0f68bbfaac35dd16
+  */
+
+  const testL1Address = "0xB12038acCE44e39dd5B2f59F0f68bbfAaC35dd16";
+
+  const provider = new ethers.JsonRpcProvider(
+    `https://sepolia.infura.io/v3/${process.env.INFURA_API_KEY}`
+  );
+
+  const testL1Contract = new ethers.Contract(
+    testL1Address,
+    getLatestABI,
+    provider
+  );
+
+  try {
+    // Call the getLatest function with CCIP read enabled
+    const result = await testL1Contract.getLatest({ enableCcipRead: true });
+    console.log({ result });
+  } catch (error) {
+    console.error({ error });
+  }
+}
+
+main().catch((error) => {
+  console.error("Error in main execution:", error);
+  process.exitCode = 1;
+});
+```
+
+This script connects to the Sepolia testnet and calls the `getLatest` function of the `TestL1` contract, demonstrating how to enable and use the CCIP-Read functionality.
+
+#### Running the Script
+
+To execute the script, follow these steps:
+
+1.  **Open a terminal** and navigate to the root directory of your project.
+
+2.  **Run the script using Hardhat** with the following command:
+
+```shell
+npx hardhat run scripts/testL1.ts --network sepolia
+```
+
+- This command will launch the `testL1.ts` script, which interacts with the `TestL1` contract deployed on the Sepolia network.
+- The script demonstrates the usage of Chainlink's CCIP-Read protocol to fetch and verify off-chain data using a Sparse Merkle Proof.
+
+#### What the Script Does
+
+- **Connects to the Sepolia Network**: Utilizes Infura as the provider to connect to the Ethereum Sepolia testnet.
+- **Interacts with the Contract**: Calls the `getLatest` function on the `TestL1` contract, showcasing how to enable and leverage CCIP-Read capabilities.
+- **Handles Off-Chain Data**: Demonstrates the retrieval and verification of off-chain data, integrating it back into the on-chain environment using CCIP.
+
+This example provides a practical demonstration of how to set up and utilize the CCIP-Read protocol within a dApp, highlighting the benefits of off-chain data fetching and proof verification.