Add comment to PR-s modifying docs that links to the published preview

[michalinacienciala]

We're adding a step to the docs.yml workflow that publishes the comment under the PR modifying the documents, after preview of the dosc gets published to the GCP bucket. The comment contains a link to the index.html page containing the table of contents. Note: we need to have ./docs/index.adoc file with right config inside to have it working in the way I described it.

Ref: https://github.com/keep-network/keep-core/pull/3211