Create a Penta demo app

[srambach]

To provide a more interesting demonstration of Penta, create a demo app based on the React seed. Desirable features include:

• Light/dark theme switcher
• RTL switcher
• Navigation between a couple of pages showing content, such as a gallery of cards or table.

Design

• [x] patternfly/patternfly-design#1281

Core Nothing needed?

React

• [ ] Create demo app

[andrew-ronaldson]

Closed as a duplicate of https://github.com/patternfly/patternfly-react-seed/issues/200