Parent ticket: https://phabricator.wikimedia.org/T339334

This ticket represents the implementation of the layout from the figma file.

ACs:

• the implemented design behaves like the screen size designs as seen in figma and as written in the parent ticket
• interactive parts like the filter, exclude empty Wikibases checkbox & pagination each loads different mock data
• UI is wired up to the actual API endpoints we built in https://phabricator.wikimedia.org/T344581

Patches:

• wbstack/ui/pull/720 | Update API endpoint for production
• wbstack/ui/pull/719 | Create a Wikibase discovery page