Add a link called "Documentation" that opens our docs (https://treehouse.sh/docs) in a new tab. Figma: https://www.figma.com/file/bGzEZo0NYHhWGJO95kwF3p/Treehouse-App?type=design&node-id=306%3A4688&t=xof3A9f6flE0HYAm-1
