Using the old search functionality, provide a top search bar that fills the main panel of the new navigation

https://projects.invisionapp.com/d/main#/console/18532170/400020224/preview

• Use the existing feature flag for the new navigation
• Use the existing search functionality, this is just to reskin the search bar into the new design
• Search should go to the existing discovery feed
• unit tests for the new search box
• e2e tests for the new search box
• responsive design for web
• light mode
• dark mode

changed due date to January 28, 2020

changed milestone to %Sprint::01/15 - Youthful Yabby

added scoped labels

changed weight to 4

added to epic &93