bugfix: apply power level in always on mode (#7)

* fixed always-on mode power level
* minor ambient light threshold + LED brightness + timing adjustments
* esp-idf-svc version update

cleanup

fine tuned: ambient light level, PWM signal, LED dimming curve, readme

- LED power level and LED dimm-down timing fine tuning

- ambient sensor fine tuning
- readme polish
- enabled [std] features in all dependencies - as we are a [std] project

timing adjustments

release preparation

readme

first release candidate

tidy