Also:
* Refactored some composed components into one inclusive HOC,
called `withUpdateButtonAttributes`.
* The HOC `withTransformSingleSelectToMultipleSelect` allows for the wrong
type to be passed to its wrapped component: if a single element is
passed, that is wrapped into an array.
This didn't play well with TypeScript which obviously complains about
the wrong type being passed to the component.
So we now allow for arrays to be passed as props and ignored by the HOC
This PR creates a new directory called `featured-items` which includes both blocks.
All the shared code lives at the top level of that directory.
Individual blocks still have their own directories, with their `block.json` and all other relevant configuration.
All the functionalities have been refactored out into their own files, accepting configuration when relevant, but mostly de-duplicating all the code.
Styles have also been refactored using mixins and extends and they mostly live in one place.
Lucio Giannotta