Add German translation of the README (README.de.md)

[alimaandev]

Summary

The project already ships translated READMEs: README.es.md (Spanish), README.fr.md (French), README.hi.md (Hindi), README.ur.md (Urdu). There is no German translation.

Goal

Add README.de.md mirroring the current English README structure, and link it from the language selector in the main README.md (the block that lists Español/Français/Hindi/Urdu).

Tasks

• Translate the full current README.md into German
• Keep the exact same headings/anchors so navigation links work
• Add a German link entry to the language selector in README.md
• Follow the structure/style of README.es.md

Acceptance criteria

• README.de.md covers all current README sections
• Language selector in README.md links to it
• No links/images broken in translation

Labels

good first issue, help wanted, documentation