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Fix printing of multi-page slides, e.g., slides with whiteboard pages.
Reveal messes up page height and page margin, we fix it.

when quitting slides while watching explain video, stop video to store correct slide number

- Works for examiner style quiz definition files ending on `-deck.yaml`
- Also produces an HTML catalog of all quizzes in the project

sizing \Vert with \left and \right does not work properly in
MathJax 3.1.4. Used to work in 3.1.2, hence we go back to that
version.

Posted the issue on MathJax: https://github.com/mathjax/MathJax/issues/2697