Add initial docusaurus setup

.gitignore

assets/postman/FIT-Connect.postman_collection.json

assets/postman/FIT-Connect.postman_environment.json

babel.config.js

docs/1_Getting_Started.md

docs/2_Quick_Reference.md

docs/3_Use_Cases_der_API.md

docs/Detailinformationen/Antrag_Event_Log.md

...nen/Authentifizierung_von_antragsempfangenden_Systemen.md

docs/Detailinformationen/Encryption.md

docs/Detailinformationen/Encryption_Key_Requirements.md

docs/Detailinformationen/Metadaten.md

docs/Detailinformationen/OAuth.md

docs/Detailinformationen/Postman.md

docs/Detailinformationen/Zustellberechtigungs-Scopes.md

docs/apis/delivery-service.mdx

docs/apis/routing.mdx

docs/authentication.md

docs/changelog.md

docs/details/authentication/users.md