Add @step to section 2

Author: KaitoMuraoka

Sources/SwiftSyntax/Documentation.docc/Tutorials/SwiftSyntax By Example.tutorial

@@ -51,6 +51,12 @@
     }
 
     @Steps {
+       @Step {
+        Configure your package. Continue to select the Package.swift file.
+            
+        @Code(name: "Package.swift", file: Package.step2.swift)
+      }
+        
       @Step {
         Add the `swift-syntax` package to the dependencies section of your 
         `Package.swift` file.