fix: add generic factory interface (#14)

* test: add L2 standard bridge interop unit tests

* fix: add tests natspec

* fix: add generic factory interface

packages/contracts-bedrock/src/L2/IOptimismERC20Factory.sol

@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.0;
+
+/// @title IOptimismERC20Factory
+/// @notice Generic interface for IOptimismMintableERC20Factory and ISuperchainERC20Factory. Used to
+///         determine if a ERC20 contract is deployed by a factory.
+interface IOptimismERC20Factory {
+    /// @notice Checks if a ERC20 token is deployed by the factory.
+    /// @param _token The address of the ERC20 token to check the deployment.
+    /// @return _remoteToken The address of the remote token if it is deployed or `address(0)` if not.
+    function deployments(address _token) external view returns (address _remoteToken);
+}