* Add support for LilyPond syntax
See: https://lilypond.org/
* Fix alpha order of LilyPond
* Add support for custom executable and options to lilypond linter
Enhances the lilypond linter with configurable options:
- Add g:ale_lilypond_lilypond_executable for custom lilypond binary path
- Add g:ale_lilypond_lilypond_options for additional command-line flags
- Refactor linter to use GetCommand() function for dynamic command building
- Add linter tests covering configuration scenarios
- Update documentation with usage examples and proper formatting
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Co-authored-by: samb0t <sambottoni@gmail.com>
