Reset change behaviour when process is interrupted.

[monomycelium]

In the systemd unit file in extra, the following line seems suspicious:

ExecStop=echo auto > /sys/class/power_supply/macsmc-battery/charge_behaviour

I think the output is not exactly being redirected:

# systemctl status asahi-battery-threshold.service
...
Aug 22 21:38:36 ace echo[17690]: auto > /sys/class/power_supply/macsmc-battery/charge_behaviour
...

It seems that systemd does not interpret the shell redirection syntax in the ExecStop directive. While spawning a shell is possible, I think it would be better for the daemon to reset charge_behaviour to its original value when it is interrupted (by intercepting SIGINT and SIGTERM). I am willing to make a PR to do so when I am free.