Replace archived kubernetes-external-secrets with external-secrets (external secrets operator)

[PatrickLaabs]

Currently, the README still covers the archived Repo for the kubernets-external-secrets.
Since this Repository has been marked as archived, the documentation should be updated, to link to external-secrets/external-secrets-operator.

Also, within the apps folder, there is archived kubernetes-external-secrets still being used.
Shall we update that, too?

WDYT?

If this is reasonable, I'd like to tackle this challenge 👍

Best
Patrick