This moves the dns setup out of the networking page into its own section.
It's currently in the same page which describes the network configuration [1]. And i'm
having a hard time deciding whether i want to migrate that one or not. So i keep an
easier path and move that one part instead.
{F4799586}
[1] https://intranet.softwareheritage.org/wiki/Network_configuration#Dns_servers
Related to T3154