enable pdf export

[alv67]

Closes #191

📑 Description

Tried in my Fork, and seems that now with PDF export enabled it works. Maybe something has been corrected.

✅ Checks

• [x] My pull request adheres to the code style of this project
• [ ] My code requires changes to the documentation
• [x] I have updated the documentation as required
• [x] All the tests have passed

ℹ Additional Information

[gmacario]

@alv67 how can I independently test this PR without messing up with https://arneis.readthedocs.io?

[alv67]

The only way I found is forking it and publishing on a new temporary readthedocs page.

This is my try: https://arneis-backup.readthedocs.io/en/rdtd-restore-pdf-export/

Another way is to use a separate branch and enabling the compilation of this branch in readthedocs, as I've done in my fork.

[gmacario]

OK, let us merge it, then