Add SwiftPM package to build dependencies for iOS (#49361)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/49361

This change adds the Package.swift file that we will use to build the dependencies for React Native

## Changelog:
[Internal] - Swift PM file to build ReactNativeDependencies

Reviewed By: cortinico

Differential Revision: D69518776

fbshipit-source-id: 85006c3c5933cc6a5fd772f7b014a823d7bb99b3