Support for Strings Catalogs (Xcode 15) (#1421)

* Support for xcode 15 string catalogs

* Add sample string catalog to Test Fixture and basic test to check that asset catalogs are added in the resources build phase

* Restore unintended changes

* Update Pull Request number for 'Support for Strings Catalogs' in changelog

* Update fixture yml generator

* Detect knownRegions based on locales in string catalogs