[DOC] Deploy Workflows in Preview Mode

User Story: As a workflow developer, I want to deploy my workflow in preview mode so that I can see how the workflow would perform in a production environment.

Additional Information: This preview mode enables the operator to build a workflow application using the OpenShift platform. The operator has an opinionated, default build pipeline embedded. We call this a preview mode because the operator won't own the build process for an enterprise-grade, production environment. Devmode and Preview mode should not be supported for production use cases.

Feature: GA

Upstream documentation: https://openshift-knative.github.io/docs/docs/latest/serverless-logic/cloud/operator/build-and-deploy-workflows.html