Web-stories ScratchCard

### Description

Implement a "Scratch to Reveal" feature in Web Stories, allowing creators to overlay a slide with an interactive layer. Users can "scratch" this layer to reveal the underlying content, enhancing interactive storytelling and user engagement.

### Alternatives Considered

Explored custom implementation using meta boxes and JavaScript within the WordPress environment. However, integrating this seamlessly within the Web Stories editor proved challenging.

### Additional Context

This feature could be leveraged for various engaging storytelling scenarios, such as revealing answers in a quiz format, uncovering hidden images, or interactive advertisements.