Sensorbox v2 AHT20+BMP280 mount remix

Remix of a temperature+pressure+humidity sensor mount dedicated for Sensorbox v2. Mounting horizontally with sensor facing downwards should yield the best possible accuracy due to natural convection. That's also how Air Gradient has its temperature sensor mounted and I treat this thing as go to benchmark when it comes to such sensors. Printing seems impossible at first glance, but using tree supports I managed to print this thing as downloaded without an issue.