Table support missing: groff tbl(1), .TS, .TE

[dmiller-nmap]

Not a really common thing, but it's causing some wonky formatting in our generated HTML docs for Npcap. Here's an example,

• formatted with man2html: https://www.tcpdump.org/manpages/pcap-savefile.5.html
• formatted with roffit: https://nmap.org/npcap/guide/wpcap/pcap-savefile.html

I may look at adding this myself later, but it's not hugely pressing at the moment.

Ref: tbl(1)