feat: add support for SwiftPM

Package.swift

@@ -0,0 +1,23 @@
+// swift-tools-version: 5.9
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+
+let package = Package(
+    name: "PerspectiveTransform",
+    products: [
+        // Products define the executables and libraries a package produces, making them visible to other packages.
+        .library(
+            name: "PerspectiveTransform",
+            targets: ["PerspectiveTransform"]),
+    ],
+    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: "PerspectiveTransform"),
+        .testTarget(
+            name: "PerspectiveTransformTests",
+            dependencies: ["PerspectiveTransform"]),
+    ]
+)

PerspectiveTransform.podspec

@@ -16,7 +16,7 @@ Pod::Spec.new do |s|
   s.social_media_url  = 'https://twitter.com/iospaulz'
   s.platform          = :ios, '12.2'
   s.swift_version     = '5.0'
-  s.source_files      = 'Pod/Classes/**/*'
+  s.source_files      = 'Sources/PerspectiveTransform/**/*'
   s.frameworks        = 'UIKit', 'CoreGraphics', 'QuartzCore'
   s.test_spec 'UnitSpecs' do |ts|
       ts.requires_app_host = false

Sources/PerspectiveTransform/Perspective+Transform.swift

@@ -5,6 +5,7 @@
 //  Created by Paul Zabelin on 2/20/16.
 //
 //
+import UIKit
 
 public extension Perspective {
     /**