feat: add support for German language (de) (#369)

Co-authored-by: Erik Berkemeyer <WRDoll770@users.noreply.github.com>

frontend/src/i18n/routing.ts

@@ -2,7 +2,7 @@ import { createNavigation } from 'next-intl/navigation';
 import { defineRouting } from 'next-intl/routing';
 
 export const routing = defineRouting({
-  locales: ['en', 'ja', 'pt-BR', 'zh-CN'],
+  locales: ['en', 'ja', 'pt-BR', 'zh-CN', 'de'],
   defaultLocale: 'en',
   localePrefix: {
     mode: 'always',

frontend/src/middleware.ts

@@ -4,5 +4,5 @@ import { routing } from './i18n/routing';
 export default createMiddleware(routing);
 
 export const config = {
-  matcher: ['/', '/(ja|en|pt-BR|zh-CN)/:path*'],
+  matcher: ['/', '/(ja|en|pt-BR|zh-CN|de)/:path*'],
 };