[HarfBuzz] the feature tag support in harfbuzz

[Akira TAGOH]

Hi Behdad and the list,

I'm not looking at the code carefully yet, so I don't know if it's
done or capable so far.

When I have ever proposed to support the Japanese related feature tags
(jp78, jp83, jp90, jp04) in Pango
(https://bugzilla.gnome.org/show_bug.cgi?id=624457), you suggested in
the off list to do it in Harfbuzz and fontconfig. is it still a way to
go right? how is it easy to implement in Harfbuzz now?

I'm still keen to see this feature to make things better and willing
to go back the work on this.
-- 
Akira TAGOH