Update docs

contracts/mocks/AccessControlCrossChainMock.sol

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+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.4;
+
+import "../access/AccessControlCrossChain.sol";
+import "../crosschain/arbitrum/CrossChainEnabledArbitrumL2.sol";
+
+contract AccessControlCrossChainMock is AccessControlCrossChain, CrossChainEnabledArbitrumL2 {
+    constructor() {
+        _setupRole(DEFAULT_ADMIN_ROLE, _msgSender());
+    }
+
+    function setRoleAdmin(bytes32 roleId, bytes32 adminRoleId) public {
+        _setRoleAdmin(roleId, adminRoleId);
+    }
+
+    function senderProtected(bytes32 roleId) public onlyRole(roleId) {}
+
+    function crossChainRoleAlias(bytes32 role) public pure virtual returns (bytes32) {
+        return _crossChainRoleAlias(role);
+    }
+}