Fix generating the PDF and improve its formatting

[vedran-kasalica]

Changes in this PR

I updated the page.yml GitHub action to generate PDFs correctly, namely:

• I migrated from docsify-pdf-converter (outdated) to docker-docsify-pdf. The new PDF generator creates a cleaner PDF that includes the TOC by default.
• GitHub action now adds the PDF as an artifact (see the fig. below)
• Pushing to Zenodo is conditional (it will not be done when the workflow is triggered manually, in that case, it only generates the PDF, for testing purposes). This could be updated to push to sanbox.zenodo.org, but that should be a separate issue.

Smaller changes:

• I added a header to the technology_overview page as it was missing (noticeable when generating a PDF).
• I also included a cover page for the PDF. I added it under Figures not to clutter the root dir, but this can be changed.

The PR resolves issues:
#270 (PDF is generated, Upload to Zenodo should be tested at the release)
#368 (TOC is now included
#369 (while the formatting is not perfect, it is much better, e.g., each section starts on a separate page, table formatting does not break, etc.)

Checklist

SIGNIFICANT changes / additions, e.g. new chapters

• I discussed my contribution in an issue and took into account feedback.

ALL contributions

• I previewed my changes locally using e.g. python3 -m http.server 4000 and confirmed they work correctly.
• I checked for broken links, e.g. using the link checker GitHub Action workflow, or locally by using docker run --init -it -v `pwd`:/docs lycheeverse/lychee /docs --config=docs/lychee.toml, at least for the files I changed.
• My name was added to the CITATION.cff file.

[egpbos]

Great PR, thank you for fixing this process and making the output much better as well! I have just one suggestion below, I'll just go ahead and commit that and then I think we can merge that. I have a few follow-up issues that I will create as well:

• Add headers to all chapters (you added one to the Technology overview page, others should have it as well).
• The PDF should have the version somewhere, preferably on the cover, but colofon or something is fine too.
• Your point: "Pushing to Zenodo is conditional (it will not be done when the workflow is triggered manually, in that case, it only generates the PDF, for testing purposes). This could be updated to push to sanbox.zenodo.org, but that should be a separate issue."

[egpbos]

Great that you also updated the action versions (also for setup-node below)!