Feature Request: Add support for fan status monitoring

[sannidhyaroy]

It'd be helpful if DietPi Dashboard would also report the fan status. Since, everyone wouldn’t have a fan installed, so this feature could be made optional that we can manually turn on and customizable (as the fan may be attached to different GPIO pins). I have an Argon40 Mini Fan HAT on my Raspberry Pi 4 Model B, and the fan works in PWM mode by adding the line dtoverlay=gpio-fan,gpiopin=18,temp=55000 to the /boot/config.txt file. There's no way to know if my fan is running or not without physically looking at the Pi 4.