Add a Image Comparison Slider Gallery Block

[richtabor]

From lozeone on WordPress.org

It would be awesome if you could add a block for a 2 image before/after gallery like here.

An interesting idea; probably wouldn't be too difficult to achieve.

Resources:

1. https://www.npmjs.com/package/react-twentytwenty
2. https://zurb.com/playground/twentytwenty