Add an under-voltage warning status

Feature Requests
#1

It would be nice to see an indication of an under-voltage condition, past or current, in to the web interface, chronometer and padd.

The results of "vcgencmd get_throttled" would be enough.

Folks are running pi-hole on systems with weak power supplies and warning them of this could avoid them thinking it is a Pi-Hole issue.

#2

This is well outside of the scope of the Pi-hole web GUI in my opinion. Linux has logs and commands for this.

But, it might be something to add to the debug log.

Edit:

That command may not be present in all varieties of Linux. Armbian, for example.

root@nanopi:/# vcgencmd get_throttled
vcgencmd: command not found

root@nanopi:/# cat /etc/os-release
PRETTY_NAME="Armbian 20.11.6 Buster"
NAME="Debian GNU/Linux"
VERSION_ID="10"
VERSION="10 (buster)"
VERSION_CODENAME=buster
ID=debian
HOME_URL="https://www.debian.org/"
SUPPORT_URL="https://www.debian.org/support"
BUG_REPORT_URL="https://bugs.debian.org/"