Regex suggester support

[selimt]

Elasticsearch supports regex suggesters as documented here:
https://www.elastic.co/guide/en/elasticsearch/reference/current/search-suggesters.html#regex

But the Search.suggest API does not support that.

A while back a PR had implemented this feature but unfortunately it has been closed:

https://github.com/elastic/elasticsearch-dsl-py/pull/1098/files#diff-a051cc028fe71537806a081bbae62c89853cc5fe07c239019b78d5a371581825R608

Any chance this can be implemented? Currently we have to resort to using the Search.update_from_dict method to modify the query in place.

Thank you.

[selimt]

Thank you!