Add link to OpenLibrary

Signed-off-by: Severin Kaderli <severin@kaderli.dev>

templates/index.html

@@ -28,7 +28,7 @@
       <tbody>
         {% for book in books %}
         <tr>
-          <td>{{book.title}}</td>
+          <td><a href="https://openlibrary.org/isbn/{{book.isbn}}">{{book.title}}</a></td>
           <td>{{book.author}}</td>
           <td>{{book.year}}</td>
           <td>{{book.pages}}</td>