termcap: Add an entry for kitty

The project is here:
https://github.com/kovidgoyal/kitty/

I created a port (which now needs updating):
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=233010

If only we could use terminfo :(

MFC after: 5 days
Approved by: bapt
Differential Revision: https://reviews.freebsd.org/D19060