Creates an OpenSearch index with optional automatic semantic enrichment for specified text fields. Automatic semantic enrichment enables semantic search capabilities without requiring machine learning expertise, improving search relevance by up to 20% by understanding search intent and contextual meaning beyond keyword matching. The semantic enrichment process has zero impact on search latency as sparse encodings are stored directly within the index during indexing. For more information, see <a href="https://docs.aws.amazon.com/opensearch-service/latest/developerguide/opensearch-semantic-enrichment.html">Automatic semantic enrichment</a>.