Shall we support date_histogram aggregation

Yes, esquery is a pretty cool project, and I wonder if we could add `date_historgram` aggregation support, see [es doc](https://www.elastic.co/guide/en/elasticsearch/reference/current/search-aggregations-bucket-datehistogram-aggregation.html).

Start with esquery's existing aggregation support and the linked Elasticsearch date histogram documentation. Determine the relevant implementation and test entry points, then confirm that date_histogram queries are generated and covered by tests.

Written by the indexing model from the issue text.