Added ArgumentParser to main project

- At Swift book's Functions and Closure section in Playgrounds (next up Objects and Classes)

Package.swift

@@ -5,11 +5,19 @@ import PackageDescription
 
 let package = Package(
     name: "swiftyfox",
+    dependencies: [
+            // other dependencies
+            .package(url: "https://github.com/apple/swift-argument-parser", from: "1.3.0"),
+        ],
     targets: [
         // Targets are the basic building blocks of a package, defining a module or a test suite.
         // Targets can depend on other targets in this package and products from dependencies.
         .executableTarget(
-            name: "swiftyfox"
-        ),
+            name: "swiftyfox",
+            dependencies: [
+                // other dependencies
+                .product(name: "ArgumentParser", package: "swift-argument-parser"),
+            ]),
+        
     ]
 )