Add support for iOS 16+

Co-authored-by: Simon Liang <simon@x-tech.io>

Author: sgade

Package.swift

@@ -5,7 +5,8 @@ import PackageDescription
 let package = Package(
     name: "PDFViewKit",
     platforms: [
-        .macOS(.v13)
+        .macOS(.v13),
+        .iOS(.v16)
     ],
     products: [
         .library(