[feature]: containerized setup enabling live preview

[mittler-works]

New feature description

A container-based solution for live previewing content will be added to make it easier for new contributors to get started.

[mittler-works]

For ref, I have already added container-based approach to the GTN training materials via this Pull Request. I want to reuse and adopt these setup to work with de.KCD training materials too.

[mittler-works]

Compose File was added.
Left Todo:

1. Documentation
2. Cleanup old docker stuff