Support @Previewable macro

[BarredEwe]

Short description 📝

In #Preview macro, can't use @Previewable or "ungrouped" views. Fix: #106

@Previewable macro not supported... e.g.

#Preview {
     @Previewable @State var count = 1
     Button("Increment \(count)") { count += 1 }
}

or ungrouped views:

#Preview {
     Text("Foo")
     Text("Bar")
}

Solution 📦

Added support for @Previewable.

Implementation 👩‍💻👨‍💻

When @Previewable property is found, the View property is wrapped around.

struct PreviewWrapperTest: SwiftUI.View {
     @State var count = 1
     var body: some SwiftUI.View {
          Text("Foo")
     }
}