Publish Skipper 2.11.x reference docs

[onobc]

The 2.11.x skipper docs are not available but referenced from spring.io at https://docs.spring.io/spring-cloud-skipper/docs/2.11.0/reference/htmlsingle/#getting-started.

Work Items

• Need to start publishing the 2.11.x reference docs again. This broke when we moved into the Dataflow monorepo.
• Fix above link that was temporarily pointed to the 2.9.x (cc: @oodamien)

[corneil]

This change involves using jfrog cli to tag the published docs artifacts with properties same as skipper project did to trigger to update of docs.spring.io