update package

Package.swift

@@ -1,8 +1,20 @@
-import PackageDescription
+// swift-tools-version: 5.8
+// The swift-tools-version declares the minimum version of Swift required to build this package.
 
+import PackageDescription
 
 let package = Package(
     name: "SidebarOverlay",
-    dependencies : [],
-    exclude: ["Tests"]
+    products: [
+        // Products define the executables and libraries a package produces, making them visible to other packages.
+        .library(
+            name: "SidebarOverlay",
+            targets: ["SidebarOverlay"]),
+    ],
+    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.
+        .target(
+            name: "SidebarOverlay"),
+    ]
 )

Sources/SidebarOverlay/SidebarOverlay.swift

@@ -0,0 +1,2 @@
+// The Swift Programming Language
+// https://docs.swift.org/swift-book