How to allow multiple selection in List in SwiftUI

Issue #878

Note that

Explicit id is needed, although Book already conforms to Identifiable
selection needs a default value

class BookViewModel: ObservableObject {
    @Published var books: [Book] = []
    @Published var selectedBooks: Set<Book> = []
}

List(selection: $viewModel.selectedBooks) {
    ForEach(viewModel.books, id: \.self) { book in
        BookRow(book: book)
    }
}