feat: create Storage.sol contract

.gitignore

@@ -9,4 +9,5 @@ broadcast
 .vscode/slither-results.json
 
 # mythril
-bin
+bin
+.DS_Store

src/Storage.sol

@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: GPL-3.0
+
+pragma solidity ^0.8.20;
+
+/**
+ * @title Storage
+ * @dev Store & retrieve value in a variable
+ * @custom:dev-run-script ./scripts/deploy_with_ethers.ts
+ */
+contract Storage {
+    uint256 number;
+
+    /**
+     * @dev Store value in variable
+     * @param num value to store
+     */
+    function store(uint256 num) public {
+        number = num;
+    }
+
+    /**
+     * @dev Return value
+     * @return value of 'number'
+     */
+    function retrieve() public view returns (uint256) {
+        return number;
+    }
+}