with lower footprint
Broken

but not that broken

Give the sensor some time to adjust
Display the applied offset on the webpage, not just the parameter

Previously, it was hardcoded to 2000 ppm, which
remains the default value.

A soft reset of the SCD30 sensor, i.e.
calling `SCD30.reset()` was added in commit
fe023428 to force an instant update of
the measurement interval after bootup.

It seems, however, that the calibration
value is not stored if the sensor is
reset before carrying out at least one
measurement after calibration.
This breaks calibration with the current code,
because the ESP (and then the SCD30) is reset
directly after calibration.

* Trying 10s instead.
* Adding warning if timestep < 10s

Forced calibration should hopefully be more reliable now.

could be useful, but hasn't been integrated
yet.