Added a multicall file.

contracts/interfaces/IMulticall.sol

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+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+/**
+ * @title IMulticall
+ * @notice This contract is a multi-functional smart contract which allows for multiple
+ * contract calls in a single transaction.
+ */
+interface IMulticall {
+    error MulticallFailed(bytes err);
+
+    /**
+     * @notice Performs multiple delegate calls and returns the results of all calls as an array
+     * @dev This function requires that the contract has sufficient balance for the delegate calls.
+     * If any of the calls fail, the function will revert with the failure message.
+     * @param data An array of encoded function calls
+     * @return results An bytes array with the return data of each function call
+     */
+    function multicall(bytes[] calldata data) external payable returns (bytes[] memory results);
+}

contracts/utils/Multicall.sol

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+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import { IMulticall } from '../interfaces/IMulticall.sol';
+
+/**
+ * @title Multicall
+ * @notice This contract is a multi-functional smart contract which allows for multiple
+ * contract calls in a single transaction.
+ */
+contract Multicall is IMulticall {
+
+    /**
+     * @notice Performs multiple delegate calls and returns the results of all calls as an array
+     * @dev This function requires that the contract has sufficient balance for the delegate calls.
+     * If any of the calls fail, the function will revert with the failure message.
+     * @param data An array of encoded function calls
+     * @return results An bytes array with the return data of each function call
+     */
+    function multicall(bytes[] calldata data) public payable returns (bytes[] memory results) {
+        results = new bytes[](data.length);
+        bool success;
+        bytes memory result;
+        for (uint256 i = 0; i < data.length; ++i) {
+            (success, result) = address(this).delegatecall(data[i]);
+
+            if (!success) {
+                revert(string(result));
+            }
+
+            results[i] = result;
+        }
+    }
+}