feat: add contract code

07_ContractDev/MyToken.sol

@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.20;
+
+import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
+import "@openzeppelin/contracts/access/Ownable.sol";
+
+contract MyToken is ERC721, Ownable {
+  uint256 private _nextTokenId = 0;
+
+  constructor()
+    ERC721("MyToken", "MTK")
+    Ownable(msg.sender)
+  {}
+
+  function mint(uint256 quantity) public payable {
+    require(quantity == 1, "quantity must be 1");
+    require(msg.value == 0.01 ether, "must pay 0.01 ether");
+    uint256 tokenId = _nextTokenId++;
+    _mint(msg.sender, tokenId);
+  }
+}

README.md

@@ -16,7 +16,7 @@ DApp 开发极简入门
 
 **第 6 讲：Next.js 部署**：[教程](./06_NextJS/readme.md)
 
-**第 7 讲：合约开发和测试**：[教程](./07_ContractDev/readme.md)
+**第 7 讲：合约开发和测试**：[教程](./07_ContractDev/readme.md) | [代码](./07_ContractDev/MyToken.sol)
 
 **第 8 讲：合约部署**：[教程](./08_ContractDeploy/readme.md)