added example for a custom ERC20 wrapper

contracts/CustomERC20Wrapper.sol

@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: MIT OR Apache-2.0
+pragma solidity 0.8.19;
+
+// This file contains show how to create a custom ERC20 Wrapper
+
+// This abstract contract provides storage padding for the proxy
+import { CustomSuperTokenBase } from "@superfluid-finance/ethereum-contracts/contracts/interfaces/superfluid/CustomSuperTokenBase.sol";
+// Implementation of UUPSProxy (see https://eips.ethereum.org/EIPS/eip-1822)
+import { UUPSProxy } from "./base/UUPSProxy.sol";
+// Superfluid framework interfaces we need
+import { ISuperToken, ISuperTokenFactory, IERC20 } from "@superfluid-finance/ethereum-contracts/contracts/interfaces/superfluid/ISuperfluid.sol";
+// for the underlying token
+import { IERC20Metadata } from "@openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol";
+
+/// @title The Proxy contract for a Custom ERC20 Wrapper
+contract CustomERC20WrapperProxy is CustomSuperTokenBase, UUPSProxy {
+
+    // This shall be invoked exactly once after deployment, needed for the token contract to become operational.
+    function initialize(
+        IERC20Metadata underlyingToken,
+        ISuperTokenFactory factory,
+        string memory name,
+        string memory symbol
+    ) external {
+        // This call to the factory invokes `UUPSProxy.initialize`, which connects the proxy to the canonical SuperToken implementation.
+        // It also emits an event which facilitates discovery of this token.
+        ISuperTokenFactory(factory).initializeCustomSuperToken(address(this));
+
+        // This initializes the token storage and sets the `initialized` flag of OpenZeppelin Initializable.
+        // This makes sure that it will revert if invoked more than once.
+        ISuperToken(address(this)).initialize(underlyingToken, underlyingToken.decimals(), name, symbol);
+    }
+
+    // add custom functionality here...
+}
+
+interface ICustomERC20Wrapper is ISuperToken {}