fixes the given warning:
Thread Performance Checker: -[AVCaptureSession startRunning] should be called from background thread. Calling it on the main thread can lead to UI unresponsiveness
which might cause a UI freeze
* chore(ios): consolidate optional argument standard
mark all optional iOS arguments as `var <name>: Type?`, following the pattern described in the documentation: https://v2.tauri.app/develop/plugins/develop-mobile/#ios
* chore: add missing Info.plist to example