feat(ui-components): introduce `Carousel`

[dhayab]

Summary

This PR introduces the Carousel UI component. It is a port of the HorizontalSlider component designed. There are a few changes:

• HorizontalSlider is now named Carousel, obv
• Class names are prefixed with ais-Carousel
• References are not forwarded anymore, Renderer is extended to allow flavors to provide their useRef implementation
• Carousel CSS colors are now SCSS variables instead of CSS variables

This PR does not implement the Carousel as a built-in layout in any InstantSearch widget for now.

Preview →

Before merging

• [x] Remove carousel import in algolia and reset SCSS files
• [x] Remove changes to getting started

FX-2817

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