Add SPM support

Author: Goos

.gitignore

@@ -7,6 +7,7 @@
 
 ## Build generated
 build/
+.build/
 DerivedData/
 
 ## Various settings

Package.resolved

@@ -0,0 +1,25 @@
+// swift-tools-version:5.3
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+
+let package = Package(
+    name: "RxIGListKit",
+    platforms: [.iOS(.v9)],
+    products: [
+        .library(
+            name: "RxIGListKit",
+            targets: ["RxIGListKit"]),
+    ],
+    dependencies: [
+        .package(url: "https://github.com/ReactiveX/RxSwift.git", from: "6.0.0"),
+        .package(url: "https://github.com/3a4oT/IGListKit.git", from: "4.0.0")
+    ],
+    targets: [
+        .target(
+            name: "RxIGListKit",
+            dependencies: ["RxSwift", "IGListKit"],
+            path: "./RxIGListKit"
+        )
+    ]
+)