Add tripadvisor (#2666)

README.md

@@ -1508,6 +1508,7 @@ API | Description | Auth | HTTPS | CORS |
 | [Transport for United States](http://www.nextbus.com/xmlFeedDocs/NextBusXMLFeed.pdf) | NextBus API | No | No | Unknown |
 | [Transport for Vancouver, Canada](https://developer.translink.ca/) | TransLink | `OAuth` | Yes | Unknown |
 | [Transport for Washington, US](https://developer.wmata.com/) | Washington Metro transport API | `OAuth` | Yes | Unknown |
+| [Tripadvisor](https://developer-tripadvisor.com/home/) | Rating content for a hotel, restaurant, attraction or destination | `apiKey` | Yes | Unknown |
 | [Uber](https://developer.uber.com/products) | Uber ride requests and price estimation | `OAuth` | Yes | Yes |
 | [Velib metropolis, Paris, France](https://www.velib-metropole.fr/donnees-open-data-gbfs-du-service-velib-metropole) | Velib Open Data API | No | Yes | No |