feat: Add a StackBlitz tutorial for sending batch transactions with Nexus SDK

[joepegler]

What

Create an interactive Stackblitz tutorial that demonstrates how to send a batch transaction using the Nexus SDK.

Why

• Provide a hands-on learning experience for users
• Showcase the simplicity and power of batch transactions
• In the docs mention the primary use case which is pairing an approval with a swap for example
• Allow users to experiment with the code without needing funds or setting up a local environment
• Enhance the documentation with an interactive example, similar to viem's approach

How

1. Develop a Stackblitz project that includes:

   • A basic React or Next.js application
   • Pre-installed dependencies: @biconomy/sdk, viem, and other necessary packages
   • A step-by-step guided tutorial in the main component or README
   • Code snippets that users can modify and run

2. Implement the batch transaction example:

   • Set up the Nexus client with a pre-configured bundler URL
   • Use a demo private key or allow users to input their own
   • Create multiple example transactions (e.g., token transfers, contract interactions)
   • Demonstrate how to bundle and send these transactions

3. Make the tutorial gas-less:

   • Use a testnet (e.g., Base Sepolia) for demonstrations
   • Implement paymaster functionality to cover gas fees

4. Integrate the Stackblitz project into the documentation:

   • Embed the Stackblitz iframe in the docs/pages/nexus/tutorials/batch.md file
   • Ensure the iframe is responsive and fits well with the existing content

5. Add instructions for users to run and interact with the Stackblitz project

6. Test thoroughly to ensure the tutorial works as expected in the Stackblitz environment

7. Update the documentation to reference and explain the new interactive tutorial

8. Consider adding a "Run in Stackblitz" button next to the existing code examples for quick access