Add CTS (#2832)

README.md

@@ -1541,6 +1541,7 @@ API | Description | Auth | HTTPS | CORS |
 | [Boston MBTA Transit](https://www.mbta.com/developers/v3-api) | Stations and predicted arrivals for MBTA | `apiKey` | Yes | Unknown |
 | [Community Transit](https://github.com/transitland/transitland-datastore/blob/master/README.md#api-endpoints) | Transitland API | No | Yes | Unknown |
 | [Compare Flight Prices](https://rapidapi.com/obryan-software-obryan-software-default/api/compare-flight-prices/) | API for comparing flight prices across platforms | `apiKey` | Yes | Unknown |
+| [CTS](https://api.cts-strasbourg.eu/) | CTS Realtime API | `apiKey` | Yes | Yes |
 | [Grab](https://developer.grab.com/docs/) | Track deliveries, ride fares, payments and loyalty points | `OAuth` | Yes | Unknown |
 | [GraphHopper](https://graphhopper.com/api/1/docs/) | A-to-B routing with turn-by-turn instructions | `apiKey` | Yes | Unknown |
 | [Icelandic APIs](http://docs.apis.is/) | Open APIs that deliver services in or regarding Iceland | No | Yes | Unknown |