docs: Add Xcode isntructions to Swift ref docs (#37839)

Add Xcode isntructions to Swift ref docs

apps/docs/docs/ref/swift/installing.mdx

@@ -20,6 +20,10 @@ custom_edit_url: https://github.com/supabase/supabase/edit/master/web/spec/supab
     - `Functions`
     - `Storage`
 
+    If you use Xcode, follow [Apple's dependencies guide](https://developer.apple.com/documentation/swift_packages/adding_package_dependencies_to_your_app) to add supabase-swift to your project. Use https://github.com/supabase-community/supabase-swift.git for the url when Xcode asks.
+
+    If you don't want the full Supabase environment, you can add individual packages, such as Functions, `Auth`, `Realtime`, `Storage`, or `PostgREST`.
+
   </RefSubLayout.Details>
 
   <RefSubLayout.Examples>