Integrate absolute humidity calculation and display it beside temperature and relative humidity

[the78mole]

As relative humidity is already a good measure about moisture effect, absolute humidity (in g/m³) is sometimes much more important, since it does not change with temperature increase and decrease. In my special case, it is about the enclosure of my 3D printer and the drybox, where I would be able to directly read the absolute humidity at the device and not always need to ask my smart home GUI about.

The calculation is not very trivial, but with some simplifications, the it does not get too complex. I already wrote an article about this topic, which should be easily adaptable to the ATC firmware: https://the78mole.de/the-magic-of-absolute-humidity/