Fix .gitignore: stop tracking ignored files

backend/lib/openzeppelin-contracts/contracts/interfaces/IERC1363Receiver.sol

@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: MIT
+// OpenZeppelin Contracts (last updated v4.9.0) (interfaces/IERC1363Receiver.sol)
+
+pragma solidity ^0.8.0;
+
+/**
+ * @dev Interface for any contract that wants to support {IERC1363-transferAndCall}
+ * or {IERC1363-transferFromAndCall} from {ERC1363} token contracts.
+ */
+interface IERC1363Receiver {
+    /*
+     * Note: the ERC-165 identifier for this interface is 0x88a7ca5c.
+     * 0x88a7ca5c === bytes4(keccak256("onTransferReceived(address,address,uint256,bytes)"))
+     */
+
+    /**
+     * @notice Handle the receipt of ERC1363 tokens
+     * @dev Any ERC1363 smart contract calls this function on the recipient
+     * after a `transfer` or a `transferFrom`. This function MAY throw to revert and reject the
+     * transfer. Return of other than the magic value MUST result in the
+     * transaction being reverted.
+     * Note: the token contract address is always the message sender.
+     * @param operator address The address which called `transferAndCall` or `transferFromAndCall` function
+     * @param from address The address which are token transferred from
+     * @param amount uint256 The amount of tokens transferred
+     * @param data bytes Additional data with no specified format
+     * @return `bytes4(keccak256("onTransferReceived(address,address,uint256,bytes)"))` unless throwing
+     */
+    function onTransferReceived(
+        address operator,
+        address from,
+        uint256 amount,
+        bytes memory data
+    ) external returns (bytes4);
+}