Add guide for setting up Auth with open source ORY Kratos

I used the React Navigation guide on auth quite extensively when writing the reference for writing how to wire the open source ORY Kratos project into React Native, the result of which can be found at https://github.com/ory/kratos-selfservice-ui-react-native.

I was wondering if it would be of interest/worth to add a section to the auth documentation covering a setup with ORY Kratos and React Native, given that both projects are open source, have a broad community, and are well maintained. I think it could help developers getting into React Native Navigation / React Native solve auth easier and with less frustration and by using Apache 2.0 licensed open source only.

I'd also be happy to check into other projects such as KeyCloak to provide a guide, however the OAuth2 set up makes this much more difficult to nail down in a couple of sections - so this could probably take a bit of time.

Beginne mit der Dokumentation zum Auth-Flow unter reactnavigation.org/docs/auth-flow und prüfe das verlinkte ORY Kratos React Native-Referenzprojekt. Prüfe, ob ein Abschnitt zu ORY Kratos in die bestehende Guide-Struktur passt, und verifiziere die Einrichtungsdetails anhand des referenzierten Projekts. Erledigt ist die Aufgabe, wenn die Dokumentation eine klare, korrekte Anleitung für die Integration von ORY Kratos in React Native bietet.