Add Swift PackageManagement support

Package.swift

@@ -0,0 +1,22 @@
+// swift-tools-version:4.0
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+import PackageDescription
+
+let package = Package(
+    name: "UTMConversion",
+    products: [
+        .library(
+            name: "UTMConversion",
+            targets: ["UTMConversion"]),
+    ],
+    targets: [
+        .target(
+            name: "UTMConversion",
+            dependencies: [],
+            path: "UTMConversion"),
+        .testTarget(
+            name: "UTMConversionTests",
+            dependencies: ["UTMConversion"],
+            path: "UTMConversionTests"),
+    ]
+)