Translate Introduction and Navigate section from english to german

[graciousgrey]

Acceptance Criteria:

• Follow the instructions in README.md to set up mkdocs locally on your system
• Translate the file: docs/user-guide/index.md to german
• Translate the file: docs/user-guide/navigate.md to german

Notes:

• Please do not rename the files
• In case there is a link to a page that is not part of the user guide (e.g. a page from the developer guide) --> link to the english version

Quality Standards:

• We will not accept translation that have been made with google translate
• Test locally that formatting (e.g. some text) is working
• Test locally that links are working
• Test locally that icons are working --> do not translate something like: :material-folder:

[clairecharles]

Hey @graciousgrey can I take this on

[clairecharles]

Hey @graciousgrey just created a pull request.