message: Add 'Usage' to docs
diff: @@ -43,3 +43,7 @@ Looking at the flow above, a common release lifecycle could be:
  - Your CI
  1. Detects the new tag by matching the git reference `refs/tags/version-.*`
  1. Builds and deploys to production for testing
  +
  +## Usage
  +
  +The plugin exports a single full-page extension `ReleaseManagerAsAServicePage`, which one can add to an app like a usual top-level tool on a dedicated route.
  