Add warning to Package.swift

* For release automation workflow, we copy Package.swift to the XCFramework repository and rename the package name from "OneSignalFramework" to "OneSignalXCFramework". Since there are multiple occurrances of `name: "OneSignalFramework"` in this file, we ONLY want to change line 7!

Author: nan-li

Package.swift

@@ -4,7 +4,7 @@
 import PackageDescription
 
 let package = Package(
-    name: "OneSignalFramework",
+    name: "OneSignalFramework", // Package name MUST be on line 7 for release automation
     products: [
         .library(
             name: "OneSignalFramework",