Add templatetags for listing textbooks.
This templatetag must be refactored to be utilized for tasks also.
[{"pk": 1, "model": "sites.site", "fields": {"domain": "example.com", "name": "example.com"}}, {"pk": 3, "model": "sites.site", "fields": {"domain": "fossee.in/pytask", "name": "PyTask "}}, {"pk": 2, "model": "sites.site", "fields": {"domain": "localhost:8080", "name": "Development Server"}}]