Chord things: alternate fingerings, and add2

[Peter Chubb]

Hi Folks,
   When notating chords for ukulele (and probably for other
   instruments too), I sometimes want to indicate a different voicing
   for a particular chord.  In published works, this is usually done
   by adding a prime or an asterisk to the chord name.  I can't work
   out a good way to do this in LilyPond.

   Here's what I mean:

\version "2.24.0"
\include "predefined-ukulele-fretboards.ly"
\storePredefinedDiagram #default-fret-table \chordmode { f' }
                        #ukulele-tuning
                        "5-1-(;5-1;5-1-);8-2;"

ch = \chordmode {f f'^\mark "*"} % <- Doesn't work
\score {
    <<
        \context ChordNames \ch
        \context FretBoards \ch
    >>
  \layout {
    \context {
      \FretBoards
      stringTunings = #ukulele-tuning
    }
  }
}