Add setting to specify a maximum delta between inside and outside temperatures

It would be nice to be able to specify a maximum delta between inside and outside temperatures, so we are not subjected to a huge temperature contrast when getting out of the car in summer. For example, if my inside temp setting was 21ºC and the "maximum delta" setting was 8ºC, the car's inside temp would stay at 21ºC up until the point where outside temp reaches 29ºC. After that, inside temp would climb up with outside temp, always keeping a 8ºC delta between the two.