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

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 :)

プリンターのセットアップに関するドキュメントと、issue で説明されている /etc/nsswitch.conf の設定を確認してください。nss-mdns のインストールと、.local プリンターを見つけるために必要な hosts 行を扱う注記を、必要に応じてリンクされたリファレンスを含めて追加してください。