Discover page UI

Figma link: https://www.figma.com/file/EgFMCBNffFiVRwaWUNyb9o/hhmi?node-id=810%3A107

The task here is to build the UIs for the discover page in storybook.

For the time being ignore the following from the screenshot above:

• The navigation bar
• The select checkboxes
• The add to list and duplicate buttons (these will come at a later version)
• The search bar at the top of the page

When it comes to styles, there's no need to make them look exactly like the screenshot. Just use whatever comes as a default from ant. Hook the component styles to the theme though, so that we can later update the theme and apply correct colors, fonts etc across the board.