Add the configuration of nss-mdns as a note for easily using printers on Void

[cezarlamann]

So, I've been fighting with CUPS here on my void installation and understood that albeit avahi-daemon service was installed, nss-mdns was not. However, installing it was not enough to get my printer to print, as I still got the error "Unable to locate printer xxxxxxx.local".

Apart from installing it, I also had to configure the /etc/nsswitch.conf, modifying the "hosts" line to be like hosts: files mdns_minimal dns mdns.

I took this info from here: https://people.math.rochester.edu/faculty/akrish11//2016/01/09/cups-unable-to-automatically-locate-printer-2.html

It might not be much, but I think it could help newcomers who still have to print stuff around :)