UI for free connector components

[ambirdsall]

New/updated UI components:

• status pill variants with "free" overlay for alpha and beta
• banners:
  • big showy marketing banner, images, the whole shebang
  • more subtle/interstitial banner for mid-connection-creation workflow
• signup modal with marketing images and stripe setup payment CTA

This new UI should all be conditionally-rendered, but the conditions can be hardcoded booleans behind a sensible API boundary during initial development. Similarly, clicking the stripe setup payment CTA can be a noop until the new endpoint it will hit is ready.

[pmossman]

Refining notes:

• Alex can split out more granular tickets from this to divide up the work