german docs translation (#18544)
* Create _config.py
* Create _toctree.yml
* Create index.mdx
not sure about "du / ihr" oder "sie"
* Create quicktour.mdx
* Update _toctree.yml
* Update build_documentation.yml
* Update build_pr_documentation.yml
* fix build
* Update index.mdx
* Update quicktour.mdx
* Create installation.mdx
* Update _toctree.yml
