added url endpoint for bookupdateview

bookshelf/urls.py

 from django.urls import path, re_path
-from .views import HomePageView, BookListView, BookDetailView, BookCreateView,\
+from .views import HomePageView, BookListView, BookDetailView, BookUpdateView, BookCreateView,\
     AuthorListView, AuthorCreateView, AuthorDetailView
 
 urlpatterns = [
@@ -7,6 +7,7 @@ urlpatterns = [
     path('books/', BookListView.as_view()),
     path('books/add/', BookCreateView.as_view()),
     path('books/<int:pk>/details/', BookDetailView.as_view(), name='bookdetailview'),
+    path('books/<int:pk>/edit/', BookUpdateView.as_view(), name='bookupdateview'),
     path('authors/', AuthorListView.as_view()),
     path('authors/add/', AuthorCreateView.as_view()),
     path('authors/<int:pk>/details/', AuthorDetailView.as_view(), name='authordetailview'),