_includes/algolia.html

<script src="https://cdn.jsdelivr.net/npm/docsearch.js@2/dist/cdn/docsearch.min.js"></script>

<script>
    docsearch({
        indexName: '{{ site.algolia.index_name }}',
        apiKey: '{{ site.algolia.search_only_api_key }}',
        inputSelector: '.searchbox-input',
        debug: true,
    });
</script>