[EXTERNAL] Cocoapods support for privacy manifest (#3772)

### Motivation
The library already includes Privacy.xcprivacy in SPM, but when used
with CocoaPods (mandatory in Flutter), these files are not exported as
the podspec does not include that file as a resource bundle.

### Description
Listing the PrivacyInfo.xcprivacy file inside the resource_bundles
specification in the podspec allows to distribute the file correctly.
Ref.
CocoaPods/CocoaPods#10325 (comment)

This GitHub issue contains the entire discussion on how to add these
xcprivacy files and is referenced in multiple places; many libraries
already follow this approach:


https://github.com/firebase/firebase-ios-sdk/blob/main/FirebaseCrashlytics.podspec
SDWebImage/SDWebImage#3649
flutter/packages#5846
Baseflow/flutter-permission-handler#1291
Baseflow/flutter-geolocator#1462

RevenueCat.podspec

@@ -31,5 +31,5 @@ Pod::Spec.new do |s|
   s.source_files = 'Sources/**/*.swift'
   s.exclude_files = 'Sources/LocalReceiptParsing/ReceiptParser-only-files/**'
 
-
+  s.resource_bundles = {'RevenueCat' => ['Sources/PrivacyInfo.xcprivacy']}
 end