chore: add `Deutsch - de-DE` language support

Current Limitation

Currently, the Asgardeo JavaScript SDK does not have support for German (Deutsch - de-DE). Users who prefer German will not see UI components translated, limiting accessibility for German-speaking users.

[!Important]
Contributors for this task should be native German speakers or have professional fluency to ensure accurate, culturally appropriate translations.

Suggested Improvement

Add German (de-DE) language support to the @asgardeo/i18n package.

Implementation Plan:

1. Create a new locale file:

   Follow https://github.com/asgardeo/javascript/blob/main/CONTRIBUTING.md#contributing-to-the-internalization-i18n-package

2. Add documentation for usage:

   • Update the SDK docs: https://wso2.com/asgardeo/docs/sdks/react/overview/

Please select the package issue is related to

@asgardeo/react, @asgardeo/nextjs

Version

current

Reporter Checklist

• I have searched the existing issues and this is not a duplicate.
• I have provided all the necessary information.
• I have verified the improvement is not available in the latest version of the package.

Lies die internen Lokalisierungs-/i18n-Anweisungen in CONTRIBUTING.md und prüfe die Locale-Dateien in @asgardeo/i18n. Aktualisiere die SDK-Dokumentation auf der verlinkten React-Übersichtsseite. Erledigt ist dies, wenn Übersetzungen für Deutsch (de-DE) verfügbar sind und ihre Verwendung für die zugehörigen Pakete dokumentiert ist.