Add simple_query_string support

[justasmalinauskas]

Hi, I have got another item to add to this library :)

https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-simple-query-string-query.html https://opensearch.org/docs/latest/search-plugins/sql/full-text/#simple-query-string

[erichard]

Thanks @justasmalinauskas 🙏