Reported in [[https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=241985|PR 241985]]
The manual page references the "vi/ex reference manual" but there is no
information about where to find that document. Add a reference to the manual in
the `SEE ALSO` section since the Project hosts a copy of it.
If D26158 gets reviewed and committed, we could close that PR.