display isni bio with existing author name

If an existing author has an isni on record and it matches an author from the isni api call,
display the isni short description to aid with identifying the appropriate author.

bookwyrm/views/books/edit_book.py

@@ -75,11 +75,14 @@ class EditBook(View):
                     for a in author_matches
                     if i["isni"] == a.isni
                 ]
+
                 isni_matches = list(filter(lambda x: x not in exists, isni_authors))
+
                 data["author_matches"].append(
                     {
                         "name": author.strip(),
                         "matches": author_matches,
+                        "existing_isnis": exists,
                         "isni_matches": isni_matches,
                     }
                 )