feat: root server DNS behavior

[agaffney]

Fixes #11

[agaffney]

$ dig @localhost -p 8053 foo.bar.dolphin.cardano

; <<>> DiG 9.18.12-0ubuntu0.22.04.2-Ubuntu <<>> @localhost -p 8053 foo.bar.dolphin.cardano
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 40850
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 2, ADDITIONAL: 2
;; WARNING: recursion requested but not available

;; QUESTION SECTION:
;foo.bar.dolphin.cardano.       IN      A

;; AUTHORITY SECTION:
dolphin.cardano.        999     IN      NS      ns1.dolphin.cardano.
dolphin.cardano.        999     IN      NS      ns2.dolphin.cardano.

;; ADDITIONAL SECTION:
ns1.dolphin.cardano.    999     IN      A       0.0.0.0
ns2.dolphin.cardano.    999     IN      A       42.42.31.31

;; Query time: 0 msec
;; SERVER: 127.0.0.1#8053(localhost) (UDP)
;; WHEN: Sat Jul 22 08:48:55 CDT 2023
;; MSG SIZE  rcvd: 207