Preflight fixup: Mark all non-structure elements as artifact

[stebrech]

Add new automatic approach in “Create and check artifacts in Acrobat”

• [ ] EN: https://accessible-pdf.info/en/basics/create-and-check-artifacts-in-acrobat/
• [ ] DE: https://accessible-pdf.info/de/basics/artefakte-in-acrobat-erstellen-und-pruefen/

Add a note in “Defining artifacts in InDesign”

• [ ] EN: https://accessible-pdf.info/en/basics/defining-artifacts-in-indesign/
• [ ] DE: https://accessible-pdf.info/de/basics/artefakte-in-indesign-festlegen/

Add a note in “Defining artifacts in Word”

• [ ] EN: https://accessible-pdf.info/en/basics/defining-artifacts-in-word/
• [ ] DE: https://accessible-pdf.info/de/basics/artefakte-in-word-festlegen/