Add option to hide battery on 'unknown' power state

[piousdeer]

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.

[ai]

Can you send PR since I do not have this hardware for tests

[piousdeer]

Apparently proxy.State reports charging even when the BAT0/status is unknown, so I'm not sure where to go with this. When battery level reaches 60%, proxy.TimeToFull is set to 0, but charging can be stopped before that, at 58 or 59 %. This probably needs to be adressed in UPower.