Add Luxembourgish open data API.

README.md

@@ -937,6 +937,7 @@ API | Description | Auth | HTTPS | CORS |
 | [Open Government, Italy](https://www.dati.gov.it/) | Italy Government Open Data | No | Yes | Unknown |
 | [Open Government, Korea](https://www.data.go.kr/) | Korea Government Open Data | `apiKey` | Yes | Unknown |
 | [Open Government, Lithuania](https://data.gov.lt/public/api/1) | Lithuania Government Open Data | No | Yes | Unknown |
+| [Open Government, Luxembourg](https://data.public.lu) | Luxembourgish Government Open Data | `apiKey` | Yes | Unknown |
 | [Open Government, Mexico](https://www.inegi.org.mx/datos/) | Mexican Statistical Government Open Data | No | Yes | Unknown |
 | [Open Government, Mexico](https://datos.gob.mx/) | Mexico Government Open Data | No | Yes | Unknown |
 | [Open Government, Netherlands](https://data.overheid.nl/en/ondersteuning/data-publiceren/api) | Netherlands Government Open Data | No | Yes | Unknown |