provide PDFs of Fassungsansicht (`dist/api/export/pdf|tex|tustep`)

[flicksolutions]

According to our discussion in discord and via Mail with Dominique:

create action/process that is manually triggered and does the following:

• [x] GET https://parzival.unibe.ch/parzdb/parzival.php?page=pdf&dreissiger=1 to https://parzival.unibe.ch/parzdb/parzival.php?page=pdf&dreissiger=827
• [x] provide PDFs in this repository for reuse in presentation-parzival

[pdaengeli]

I meant to have opened this, but never submitted…

Here's the implementation plan:

• Create wrapper script
• Embed existing command
• Optionally fetch pdf/tex/tustep files from existing interface and make them available in appropriate directory (dist/api/export/pdf, dist/api/export/tex, dist/api/export/tustep)

[pdaengeli]

Something went wrong with tex exports, will check later.