Add German author guide translation

[moritz-htk]

The Issue

Currently, the wiki's author guide and technical documentation are only available in English. To make the platform more accessible to German-speaking mod developers and contributors, a German translation of the guide is needed.

The Proposal

This pull request adds a complete German translation of the Author Guide. The translation files have been added to the documentation content directory at: /apps/docs/content/de/

All pages that also exist in the English guide have been translated, including:

• Introduction & Getting Started
• Folder Structure: Including Overview, Wiki metadata, Pages (Content & Documentation), Folder metadata, Homepage, Assets, Translations, and Game Data.
• Tools: Covering Gradle integration, Local preview, Game data exports, and Third-party tools.
• Portal: Instructions for Publishing and Project management.
• Components: Common and Interactive components

Additionally, I have updated lang.ts to include German in the language selection, so users can switch the language.

The translation retains the original MDX structure and formatting to ensure consistency with the existing English guide.

Possible Side Effects

Due to the change in lang.ts, there may be routing issues, although I did not encounter any problems during local testing.

What I noticed is that the German index.mdx page displays a gray bar on the left in my local preview, which is not there on the English page.

View image

Alternatives

An alternative would have been using machine translation (like Google Translate) directly in the browser, but a manual, context-aware translation provides much better technical accuracy and a more natural tone for the developer community.

[vercel]

@moritz-htk is attempting to deploy a commit to the Sinytra Team on Vercel.

A member of the Team first needs to authorize it.