How do I add fingering for chords

[Kevin Dalley]

Can I add fingering information for ChordNames when chords are entered
using chordmode?  Fingering when using staffs might be interesting as
well.  Since this is for an accordion, a single finger is often
sufficient, and I don't need 1 number per note.

\version "2.9.19"
\include "english.ly"
#(set-global-staff-size 20)
harmonies =
\relative c, {
  \chordmode {
    \time 4/4
    c1:m c:m d:m7 e:m f2:m g:7 \bar "||"
  }
}

\score {
  <<
    \context ChordNames {
     \harmonies
    }
      \context Staff = lower {
        \clef treble
        \key c \minor
                                %      \lower
        \harmonies
      }
  >>
  \layout {
    \context { \GrandStaff \accepts "Lyrics" }
    \context { \Lyrics \consists "Bar_engraver" }
  }
}