Add example for batch transactions using Aptos SDK

[Akk525]

Description

This pull request adds a new example, batchTransactions.js, to the examples/javascript directory. The example demonstrates how to perform batch transactions using the Aptos SDK, showcasing the process of sending multiple transactions sequentially in a script. This example is designed to help developers optimize workflows that involve multiple on-chain operations.

Test Plan

1. Run the script using the following command:

   node examples/javascript/batchTransactions.js
   
2. Verify the following:
   - The script successfully submits multiple transactions to the Aptos Devnet.
   - Transaction hashes are displayed in the console.
   - Each transaction hash can be validated on the [Aptos Devnet Explorer](https://explorer.devnet.aptos.dev/) by searching     for the transaction hash.

### Related Links
No related issues or pull requests.

### Checklist
- [x] Have you ran `pnpm fmt`?  
  **Yes**, the code has been formatted using `pnpm fmt`.
- [ ] Have you updated the `CHANGELOG.md`?  
  **No**, as this is an addition to the examples directory and does not modify core functionality.

[gregnazario]

We generally have avoided the JavaScript examples, just because we already are building them in TypeScript, which tends to have better practices / showing how to manage types (where JavaScript you can omit them).

I'm curious have you seen this example in TypeScript?

It uses a transaction worker thread to manage the batch send, which might not be exactly what you want.

I'd love feedback as well if JavaScript examples are important rather than just TypeScript.

cc @0xmaayan

[gregnazario]

If you're looking to send multiple transactions at once, should probably do these in parallel and handle the sequence number appropriately.

Suggested change

	// Loop through each transaction payload, send the transaction, and track its hash
	for (const txPayload of transactions) {
	const txHash = await sendTransaction(txPayload); // Send the transaction and get its hash
	transactionHashes.push(txHash); // Store the transaction hash in the array
	console.log(`Transaction submitted with hash: ${txHash}`); // Log the transaction hash
	}
	// Loop through each transaction payload, send the transaction, and track its hash
	const promises = transactions.map((payload) => sendTransaction(payload)); // Handle errors here
	const transactionHashes = Promise.all(promises);
	console.log(`Transactions submitted with hashes: ${JSON.stringify(transactionHashes)}`); // Log the transaction hashes
	}