public function category($id)
 {
     $categories = Category::all();
     $category = Category::find($id);
     $books = $category->books()->where('published', 1)->get();
     return view('store.category', compact('category', 'categories', 'books'));
 }
 public function destroy($id)
 {
     Category::find($id)->delete();
     return redirect()->route('admin.categories.index');
 }