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