Include workshop materials (and other materials) on the fly

What

Download content from external (HIFIS maintained) repos and include them as (public) sub-pages beyond hifis.net. First demonstrator/stub for the OOP workshop.

Why

First use-case: Publicly include specific course material. Likewise applicable for techdoc, HIFIS newsletter, Teaser Video, Reports, etc etc

Where

• Review here for stub of course materials index page. 👈
• Some Sources:
  • workshop-materials/
  • download script collection (one-by-one so far)

---

To do

• Added /workshop-materials folder and started index
• First version of automatically downloading the workshop materials in subsequent folders
  • Did same for HIFIS Teaser video and techdoc
• Added link to that page from the "learning materials" page
• @erxleb87 First review + Check if this way of materials inclusion is principally okay and worth to be further worked on

If that way of materials inclusion is principally okay:

• FE: Add more WS materials analogously
• FE: Complete and refine index
• More linking to the index page from other pages, e.g., education page, events.hifis.net, etc
• UJ: Do same way of incorporation for the HIFIS News letter (probably in separate MR)
• Fix or somehow ignore remaining errors:
  • Seemingly html/link checker errors stem from errors of the included repos themselves. So, either correct there or ignore here.
• ~~doc and doc/ do not yet seem to work alike. Check if this is a review app problem. @jandt-desy ~~
• Discuss policy: Currently, numerous external projects are incorporated with their respective newest builds. For accountability, it may be (in future) reasonable to include specific/versioned builds only. Propose to add a disclaimer in readme.md "In future, inclusion of external data, repositories, or artifacts may become subject to obligatory review for update." or alike.

---

Before merging:

• Delete outdated/old links from index page
• @jandt-desy Remove extra treatment for /doc inclusion on hifis.net server, since this is now included here.
• Add pipeline trigger to at least techdoc.