Problem/Motivation
Following up on the commit of #1741498: Add a mobile preview bar to Drupal core.
Remaining tasks
#1920454: Add an orientation toggle to the responsive preview feature so that a page may be previewed in portrait and landscape modes
#1920564: Decide what else is in scope for responsive preview and ensure contrib can extend what isn't
#1920694: Indicate which device in the Responsive Preview list is active