Feature request: report charging status

Report battery charging status to host devices, i.e. charging/discharging.

Implementation proposal:

Read charging status using the Zephyr charger API from a chosen zmk,charger device. If zmk,charger is not set, always report discharging.

Add a new zmk,charger-gpio driver that provides charger API by reading a GPIO. This would allow using charger ICs without an I2C/SPI interface.

I have interest in implementing this after ZMK completes upgrading Zephyr version, and maybe after #2938 is merged.

Provide feedback