struct ContentView: View {
   @Environment(ApplicationData.self) private var appData

   var body: some View {
      NavigationStack {
         List(appData.userData) { book in
            CellBook(book: book)
         }
         .navigationTitle(Text("Books"))
         .toolbar {
            ToolbarItem(placement: .topBarTrailing) {
               Button("Email", systemImage: "envelope", action: {
                  print("Read Emails")
               })
               .buttonStyle(.plain)
               .foregroundStyle(.black)
               .padding(5)
               .background(.yellow)
               .badge(5)
            }
            .sharedBackgroundVisibility(.hidden)
         }
      }
   }
}