add erc20 mock for testing

Author: skutcher

contract/mocks/MockERC20.sol

@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.26;
+
+import {ERC20} from "@openzeppelin/contracts/token/ERC20/ERC20.sol";
+
+contract MockERC20 is ERC20 {
+    constructor(string memory n, string memory s) ERC20(n, s) {}
+
+    function mint(address to, uint256 amount) external {
+        _mint(to, amount);
+    }
+}