fix(autocomplete-js): display warning when there are more than one instances of autocomplete

[dhayab]

While autocomplate can technically render multiple instances in the same document, in practice it results in inconsistent behavior when a user interacts with them.

This is because we currently bind pointer events on Window to determine whether a panel should be closed after a user clicks outside of it. This only works for one of the autocomplete added to the document.

Until we find a way to handle that, and to make customers aware of this limitation, this PR displays a warning in dev when there are more than a single instance of Autocomplete on a document.

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Sandbox	Source
@algolia/autocomplete-example-github-repositories-custom-plugin	Configuration
@algolia/autocomplete-example-instantsearch	Configuration
@algolia/autocomplete-example-playground	Configuration
@algolia/autocomplete-example-preview-panel-in-modal	Configuration
@algolia/autocomplete-example-react-renderer	Configuration
@algolia/autocomplete-example-starter-algolia	Configuration
@algolia/autocomplete-example-starter	Configuration
@algolia/autocomplete-example-reshape	Configuration
@algolia/autocomplete-example-vue	Configuration

[sarahdayan]

I realized that we don't document destroy in the docs. Should we add an entry here so we can link it in the warning?