Add AsciiDoc workshop exercises for software architecture documentation

This issue proposes adding a set of structured workshop exercises to help participants learn AsciiDoc for software architecture documentation.

The exercises will focus on:
1. Setting up arc42 with docToolchain
2. AsciiDoc basics in the context of architecture documentation
3. Creating architecture diagrams with PlantUML and C4
4. Documenting architecture decisions (ADRs)
5. Quality goals and scenarios
6. Collaboration and CI/CD integration

All exercises will be created as AsciiDoc files with examples, tasks, and bonus challenges.

This will provide workshop participants with a structured learning path that combines AsciiDoc fundamentals with practical architecture documentation concepts.