Add Nager.Date Public holiday project with api (#756)

* Add Nager.Date Public holiday project with api

* Update README.md

README.md

@@ -135,6 +135,7 @@ API | Description | Auth | HTTPS | CORS |
 | [Hebrew Calendar](https://www.hebcal.com/home/developer-apis) | Convert between Gregarian and Hebrew, fetch Shabbat and Holiday times, etc | No | No | Unknown |
 | [Holidays](https://holidayapi.com/) | Historical data regarding holidays | `apiKey` | Yes | Unknown |
 | [LectServe](http://www.lectserve.com) | Protestant liturgical calendar | No | No | Unknown |
+| [Nager.Date](https://date.nager.at) | Public holidays for more than 90 countries | No | Yes | No | 
 | [Namedays Calendar](https://api.abalin.net/) | Provides namedays for multiple countries | No | Yes | Yes |
 | [Non-Working Days](https://github.com/gadael/icsdb) | Database of ICS files for non working days | No | Yes | Unknown |
 | [Russian Calendar](https://github.com/egno/work-calendar) | Check if a date is a Russian holiday or not | No | Yes | No |