add swiftpm support

Author: cntrump

Package.swift

@@ -0,0 +1,29 @@
+// swift-tools-version:5.0
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+import PackageDescription
+
+let package = Package(
+    name: "Masonry",
+    platforms: [
+        .macOS(.v10_11),
+        .iOS(.v9),
+        .tvOS(.v9)
+    ],
+    products: [
+        // Products define the executables and libraries a package produces, and make them visible to other packages.
+        .library(
+            name: "Masonry",
+            targets: ["Masonry"])
+    ],
+    targets: [
+        // Targets are the basic building blocks of a package. A target can define a module or a test suite.
+        // Targets can depend on other targets in this package, and on products in packages this package depends on.
+        .target(
+            name: "Masonry",
+            path: ".",
+            exclude: ["Masonry/Info.plist"],
+            sources: ["Masonry"],
+            publicHeadersPath: "Masonry"
+        )
+    ]
+)