[DOCS] Include "endpoints are enrolling" message in onboarding docs #271
Description
META: https://github.com/elastic/security-team/issues/238
Background:
When the user first stands up an Agent, there is a lag time before the Endpoint is installed and sends its first docs to ES. The lag time is also increased with the transform. To help with UX and user feedback, we should show a notification that Endpoints are enrolling to let them know that progress is being made.
Show a message on Endpoint list that says "Endpoints are enrolling, etc" when Agents are up, but Endpoints haven't sent docs to ES yet
