manpage.rb: space ellipses more pleasantly

[g-branden-robinson]

asciidoctor/lib/asciidoctor/converter/manpage.rb

Line 707 in fd0e92a

.gsub(EllipsisCharRefRx, '...') # horizontal ellipsis

groff_man_style(7):

   Portability
...
     \|        Thin space (one‐sixth em on typesetters, zero‐width on
               terminals); a non‐breaking space.  Used primarily in
               ellipses (“.\|.\|.”) to space the dots more pleasantly on
               typesetters like dvi, pdf, and ps.

The \| escape sequence is universally portable to roff implementations; it appeared in Joe Ossanna's CSTR #54 in 1976.

[mojavelinux]

The .\|.\|. sequence seems to be used by many of the common man pages on Linux (grep being one example), so there's precedence for using it. I think this is something we can add in 2.1.x.