Add SPM support

Author: César Vargas Casaseca

Package.swift

@@ -0,0 +1,25 @@
+// swift-tools-version:5.0
+
+/**
+ *  Warhol
+ *  Copyright (c) César Vargas Casaseca 2020
+ *  Licensed under the MIT license (see LICENSE file)
+ */
+
+import PackageDescription
+
+let package = Package(
+    name: "Wyler",
+    platforms: [
+      .iOS(.v11)],
+    products: [
+        .library(
+            name: "Wyler",
+            targets: ["Wyler"]
+        )
+    ],
+    targets: [
+        .target(name: "Wyler",
+                path: "Wyler/Wyler")
+    ]
+)