move er721-101 to solidity dir

solidity/erc721-solidity-101/hardhat.config.js

@@ -0,0 +1,19 @@
+/**
+* @type import('hardhat/config').HardhatUserConfig
+*/
+require('dotenv').config();
+require("@nomiclabs/hardhat-ethers");
+
+const { API_URL, PRIVATE_KEY } = process.env;
+
+module.exports = {
+   solidity: "0.7.3",
+   defaultNetwork: "rinkeby",
+   networks: {
+      hardhat: {},
+      rinkeby: {
+         url: API_URL,
+         accounts: [`0x${PRIVATE_KEY}`]
+      }
+   },
+}