feat: Add Hardhat config, MockERC20 and tests for Smart Contract

contracts/MockERC20.sol

@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.20;
+
+import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
+
+contract MockERC20 is ERC20 {
+    constructor(string memory name, string memory symbol) ERC20(name, symbol) {}
+
+    function mint(address to, uint256 amount) public {
+        _mint(to, amount);
+    }
+}