extract meta data from lilypond compilation

* write that as yaml file next to the other outputs
* extract lyrics

public_includes/layout_bottom.ily

@@ -72,6 +72,13 @@ TEXT = \markuplist {
     (if paper (set! $defaultpaper paper))
   )
 
+  ;; Meta-Daten des Liedes als YAML neben die Ausgabedatei schreiben
+  ;; (<ly:parser-output-name>.yml, landet wie das PDF relativ zum Arbeitsverzeichnis)
+  (when (and (defined? 'yaml-export-enabled) yaml-export-enabled)
+    (scm->yml-file
+      (string-append (ly:parser-output-name) ".yml")
+      (extract-song-data HEADER MUSIC TEXT_PAGES)))
+
   ;; ChordPro export: Store filename and extract metadata from basicSongInfo FIRST
   (when (and (defined? 'chordpro-export-enabled) chordpro-export-enabled)
     ;; Use ly:parser-output-name which returns the output basename