Add skill knowledge for handling pesky view modifiers not available on all platforms

[edorphy]

I think you did this in one of your portfolio series videos.

I'd like to see the agent have the knowledge to introduce view modifier wrappers when APIs don't exactly match across platforms. When something isn't available, suggest conveniences to shift where compiler directives live. And for new APIs, introduce extensions that will be removed once the OS target is high enough.

If you need more details let me know.

We have all written code like this before... potentially all over our codebases.

#if os(iOS)
  .platformSpecificDetail1()
#elseif os(macOS)
  .platformSpecificDetail2()
#elseif os(visionOS)
  .platformSpecificDetail3()
#endif