fix build error for training files

[RolandJentschETAS]

This pull request makes several improvements to the Sphinx training documentation build process and the structure of the training content files. The main changes include refining how certain files are excluded from the Sphinx build, updating metadata in Markdown files to improve navigation and suppress warnings, and enhancing the formatting of module and quiz links for consistency and compatibility.

Sphinx build configuration and file exclusion:

• Updated process/conf.py to clarify that exclude_patterns are not used directly; instead, file exclusion is handled in a Sphinx build hook, improving compatibility when building from other repositories. The previous exclude_patterns setting is now commented out with explanatory comments.

Markdown metadata and navigation improvements:

• Added orphan: true and suppress_warnings: ["myst.xref_missing"] metadata to the index.md files in both the requirements engineering training and the templates, as well as orphan: true to all module and quiz files. This prevents Sphinx warnings about unreferenced pages and missing cross-references, making the build cleaner and navigation more robust. [1] [2] [3] [4] [5] [6] [7] [8] [9]

Formatting and link consistency:

• Changed Markdown links for modules and quizzes in the overview tables to HTML <a href="..."> tags in both the requirements engineering and template training index.md files. This improves link rendering and compatibility with Sphinx/Myst parser. [1] [2]

[RolandJentschETAS]

See #757

[github-actions]

The created documentation from the pull request is available at: docu-html