Added German Translation

[get-colibri]

This pr was created with colibiri, it includes changes proposed by:
1 Users in README_de.md

Beyond the propsosed changes, 2 annotations had been created.

Open the Document in Colibri to read more.

---

What is Colibri?

Colibri is a real-time collaborative Markdown editor that lets you work in sync and async.

With Colibri, you can:

• Create, annotate, and suggest changes with a Google Docs–like experience
• Discuss RFCs, documentation, or any Markdown files with your team
• Collaborate directly on Markdown in your repository

It's designed to make reviewing and editing documents faster, clearer, and more interactive.

[pszymkowiak]

Thanks for the German translation! Looks good. Please rebase on develop:

git fetch upstream develop
git rebase upstream/develop
git push --force-with-lease

[pszymkowiak]

Also please add DCO sign-off:

git commit --amend -s --no-edit
git push --force-with-lease