Unbound: Hyperlocal root config

[MikeBishop]

RFC 8806 recommends running a local replica of the root zone (and localroot.isi.edu advocates additional zones) in order to provide improved performance and privacy for users of a recursive resolver. By fetching the full zone once (via AXFR) and periodically updating it (via IXFR), recursives generate less load on the root servers and satisfy their own queries more quickly.

This adds a checkbox in the Advanced section of the Unbound config that, if checked, injects the appropriate config to host local copies of ., .arpa., and .root-servers.net..