doc: add docstring for WeatherAPI.getTemperature

src/main/java/eirb/pg203/WeatherAPI.java

@@ -40,6 +40,9 @@ public class WeatherAPI implements WeatherDataAPI{
         return new JSONObject(result.toString());
     }
 
+    /**
+     * @param day Day, 0 ≤ day ≤ 14
+     */
     @Override
     public Temperature getTemperature(int day, String city) throws IOException {
         JSONObject result = fetchWeather(day+1, city);