ValueOnly: Support dateTime Range and not only string

[BirgitBoss]

Is your feature request related to a problem? Please describe. see https://github.com/admin-shell-io/aas-specs-api/pull/222/files#r1653646603

In case of date range it could help to be more precise and define a DateValue:

DateValue: 
  type: string
  format: date-time

Without that every date format could be used and would be be not interoperable.