sysutils/catsit: New port: Process supervisor

The catsitd daemon is a process supervisor for FreeBSD and OpenBSD.
It is designed to supervise processes with the following behavior:

* The process runs in the foreground, not as a daemon.
* The process logs to standard output or standard error.
* The process handles errors by exiting and expects to be
  restarted.
* The process indicates its reason for exiting with sysexits(3).

WWW: https://git.causal.agency/catsit/

PR:		266233