SwissInfo - WWII Radio Bulletins importers

[piconti]

Similarly to #147, Create the importer for SwissInfo Radio bulletins.

The WWII radio bulleting data is already on the EPFL NAS, unfortunately it's in text-embedded pdf format, so the OCR first needs to be extracted from the PDF.

Action points for this issue are:

• Look at how the OCr text can be extracted from the pdfs and what output formats it would create.
  • Tetml? Other tools? Look at libraries that do this
  • Explore the solutions proposed by swissAI: PDF-Extract-Kit and docling
• Based on the structure of the resulting OCR data, identify if the Radio Bulletin CI schema would work for it
• Implement an importer that creates radio-bulletin content-items
• Document and comment the code relating to this.