Isolated percent repeats

Isolated percents can also be printed.

\version "2.24.0"

makePercent =
#(define-music-function (note) (ly:music?)
   "Make a percent repeat the same length as NOTE."
   (make-music 'PercentEvent
               'length (ly:music-length note)))

\relative c'' {
  \makePercent s1
}