Feature/auto mass payouts

[KelvinTrinhSG]

Description

Add a new example called auto-mass-payouts demonstrating how to automate ERC20 token distribution to multiple wallets on BNB Chain using Hardhat and Node.js backend.

This example includes:

• A deployable ERC20 token contract
• A MassPayout smart contract for batch transfers
• A REST API built with Express.js to trigger payouts
• A .env-based configuration system
• Sample scripts for deployment and test runs

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

• ✅ Deployed the ERC20 token contract (MyToken.sol) and the MassPayout contract to BNB Chain Testnet using Hardhat
• ✅ Transferred ERC20 tokens from the deployer's wallet to the MassPayout contract to ensure it holds enough balance
• ✅ Ran the run-payout.js script and also tested the /payout API endpoint through both curl and Postman, using a JSON body with recipient wallets and token amounts
• ✅ Verified the transaction success status on https://testnet.bscscan.com using the returned tx hash
• ✅ Confirmed that each recipient wallet correctly received the specified amount of tokens by checking balances on BSCScan
• ✅ Repeated payout tests with different recipient/amount configurations to validate flexibility
• ✅ Confirmed that improper input (e.g. length mismatch) triggers appropriate errors

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (README.md)
• My changes generate no new warnings
• I have added tests or verified results manually on testnet
• New and existing scripts run locally without error

[KelvinTrinhSG]

✅ Successfully tested the backend payout API using Postman.

The transaction was triggered by a POST /payout request to the Express backend with a JSON body containing recipient wallet addresses and token amounts.

📄 You can verify the result here on BSC Testnet Explorer:
🔗https://testnet.bscscan.com/tx/0x70fd7d9383b1842d9d48c1da3097f8c21cac3fe3b0aec67e9cfec9399e1abd90