Added Thirukkural API in Books category

Added Thirukkural API in Books category -- API returning all 1330 Thirukkural poems  and explanation in Tamil and English

README.md

@@ -121,6 +121,7 @@ API | Description | Auth | HTTPS | CORS |
 | [Open Library](https://openlibrary.org/developers/api) | Books, book covers and related data | No | Yes | No |
 | [Penguin Publishing](http://www.penguinrandomhouse.biz/webservices/rest/) | Books, book covers and related data | No | Yes | Unknown |
 | [Rig Veda](https://aninditabasu.github.io/indica/html/rv.html) | Gods and poets, their categories, and the verse meters, with the mandal and sukta number | No | Yes | Unknown |
+| [Thirukkural](https://api-thirukkural.web.app/) | 1330 Thirukkural poems and explanation in Tamil and English | No | Yes | Yes |
 | [Vedic Society](https://aninditabasu.github.io/indica/html/vs.html) | Descriptions of all nouns (names, places, animals, things) from vedic literature | No | Yes | Unknown |
 
 **[⬆ Back to Index](#index)**