textproc/docproj: Add Hugo/Asciidoctor dependencies

This just adds the new dependencies for building the doc tree with
Hugo/Asciidoctor, as we still have the legacy docs available, will be
kept the former dependencies for a little while.

PR: 253518
Submitted by: Yasuhiro Kimura, Dries Michiels
Reviewed by: 0mp, adamw, dbaio, debdrup, lwhsu
Approved by: doceng (bcr, maintainer)
Differential Revision: https://reviews.freebsd.org/D28609