Add support for building with Swift Package Manager

Author: andre4ik3

.gitignore

@@ -2,3 +2,5 @@
 build/
 *.pkg
 *.zip
+/.build
+/.swiftpm

Package.swift

@@ -0,0 +1,18 @@
+// swift-tools-version: 5.8
+
+import PackageDescription
+
+let version = "0.5"
+let package = Package(
+    name: "desktoppr",
+    targets: [
+        .executableTarget(
+            name: "desktoppr",
+            path: "desktoppr",
+            exclude: [
+                "Info.plist",
+                "ToDo.markdown"
+            ]
+        ),
+    ]
+)