Update macOS deployment target to v15

Raised the minimum macOS deployment target from v14 to v15 in Package.swift to align with updated platform requirements.

Author: rismay

Package.swift

@@ -20,7 +20,7 @@ let package = Package(
   name: "WrkstrmNetworking",
   platforms: [
     .iOS(.v16),
-    .macOS(.v14),
+    .macOS(.v15),
     .macCatalyst(.v15),
     .tvOS(.v16),
     .visionOS(.v1),