Some users want a top level document title bookmark in PDF output. We should enable this per configuration using defaults derived from document title.
Set the default "markup" of that bookmark to bold, but allow to override per some ..._bold: false or similarly.
Example resulting in bookmatter.tex:
\pdfbookmark[startatroot,bold]{The Document Title Endlessly Winding Lines}{doctitle}
Implemented in version 2023.11.20