fix: Improve Solidity Contract with Donation Function and Underflow P…

…rotection

- Introduce new functionality to transfer ETH in `helloworld.sol`
- Add fallback function `receive` for donating ETH
- Enhance `donate` function with Transfer event emission and Ether acceptance
- Implement underflow protection in insertion sort function for bug fix
- Make significant changes to `helloworld.sol` for overall improvement

solidity/WTF/helloworld.sol

@@ -18,6 +18,11 @@ contract HelloWeb3 {
     // event is used to log the transaction
     event Transfer(address indexed from, address indexed to, uint256 value);
 
+    // transfer all ETH to another contract
+    function migrateTo(address payable _to) public onlyOwner {
+        _to.transfer(address(this).balance);
+    }
+
     function changeOwner(address newOwner_) external onlyOwner {
         owner = newOwner_;
     }
@@ -55,6 +60,11 @@ contract HelloWeb3 {
         }
     }
 
+    // donate ETH to this contract
+    receive() external payable {
+        this.donate();
+    }
+
     function insertionSort(
         uint[] memory arr
     ) public pure returns (uint[] memory) {