Write FFmpeg FFMETADATA1 chapter files for LibriVox audiobooks: contiguous ms chapters, HTML-cleaned and…

Write FFmpeg FFMETADATA1 chapter files for LibriVox audiobooks: contiguous ms chapters, HTML-cleaned and…: a task in pool-desk (Harbor dataset). We are muxing five public-domain audiobooks into single files and need an FFmpeg chapter-metadata file for each one, built from our section list.