feat(instantsearch.js): introduce `carousel` template

[sarahdayan]

This introduces the carousel template and implements the layout template in Recommend widgets.

https://algolia.atlassian.net/browse/FX-2818

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Sandbox	Source
example-instantsearch-getting-started	Configuration
example-react-instantsearch-getting-started	Configuration
example-react-instantsearch-next-app-dir-example	Configuration
example-react-instantsearch-next-routing-example	Configuration
example-vue-instantsearch-getting-started	Configuration