add URL property

src/main/java/sensor2graph/Sensor.java

@@ -112,6 +112,11 @@ class Sensor {
 				new JsonPrimitive("\""+ rec.get("description") +"\"")
 			);
 		}
+		add_attribute(body,
+			"9",
+			"URL",
+			new JsonPrimitive("\"https://sensordata.open-forecast.eu/\"")
+		);
 		// add_attribute(body,
 		// 	"21.T11148/f76ad9d0324302fc47dd",
 		// 	"\"instrument type string\""