[Feature request] Create TOC from the input's outlines (bookmarks)

That's me giving up. I liked very much your tools, but I couldn't figure out a way to submit a PR for this feature.

Fitz and Fitzutils both seem to have tools that would trivialize such a feature. A flag like -b (for bookmarks) and invoking and processing `fitz.Document.get_toc(False)` probably could do the trick, except that going back and forth from fitz.py to fitzutils.py to pdfexmeta.py and app.py confused me to a point I couldn't even print this single line!

Well, I'm just a beginner, but maybe you'll have some spare time for implementing this.

Thank you!

Start by tracing the existing flow between fitz.py, fitzutils.py, pdfexmeta.py, and app.py, then inspect the CLI option handling. Check how fitz.Document.get_toc(False) exposes input bookmarks and determine where a -b option would fit. Done means the CLI can generate a TOC from the PDF's existing outlines.

Written by the indexing model from the issue text.