feat(specs): add playground

[Haroenv]

goal of this is to replace storybook at term, once it's all working as we expect.

What's currently done:

An example done for Breadcrumb using Sandpack for all flavours, using npm/codesandbox to get the package contents

What still should be done

• fix ssr styling (somehow dark first)
• local package (and built package for site)
• some styling:
  • Maybe tabs for the examples
  • actually differentiate between "focused widget" and the regular app
  • "full screen mode"
• see if we really need only one example per widget, otherwise design for multiple examples