Add option to hide battery on 'unknown' power state

On my Lenovo Legion laptop, and probably on other Lenovo laptops, when battery conservation mode is enabled and the battery level reaches the threshold (which can be 58 to 60 %), `/sys/class/power_supply/BAT0/status` reports `Unknown`. It'd be great if this extension supported this to avoid having to manually change the maximum charging level from 100% to 58% and vice versa whenever the conservation mode is toggled.