Repeat improvements (LilyPond Changes)

### Repeat improvements

- The new music functions `\%` and `\*` serve as abbreviations for `\repeat percent` and `\repeat unfolded`.

  >     \%3 \*4 cis''4

- `\repeat volta` alternative endings no longer create invisible bar lines. This may affect line breaking, horizontal spacing, and `VoltaBracket` length where an alternative begins or ends without a bar line. In the case of an undesired change, try adding `\bar ""` or another command that creates a `BarLine` at that point.
- Using the new `printInitialRepeatBar` property, it is possible to print a start repeat bar line, automatically, at the beginning of the piece.

- The volta number position relative to the the volta bracket can now be adjusted with the `volta-number-offset` property of `VoltaBracket`.

#### LilyPond Changes v2.26.0 (stable-branch).

- Major changes in LilyPond
  - Notes for source compilation and packagers
- New for musical notation
  - Pitches improvements
  - Rhythm improvements
  - Expressive mark improvements
  - Repeat improvements
  - Editorial annotation improvements
  - Text and font improvements
- New for specialist notation
- Miscellaneous improvements