Namespace vendored Xcframeworks per app #23

At the time of writing, we have only one test app, but in a mono-repo with more than one (which I imagine we'll get at some point - with individual examples, etc) our host package will be sharing the ./xcframework directory across multiple apps. Running "pod install" in one followed by "pod install" in another will result in deletions of the previous Xcframeworks on the second run, which is impractical. If we instead found a way to store the vendored Xcframeworks in the app's ios/Pods directory, we'd be able to avoid this "overriding" behaviour when switching between two (or more) apps.