[v1.15.1] Add support for conversational search

This issue follows the changes related to Meilisearch v1.16.0 mega issue.

Description

Add the necessary methods to interact with the chats API. You can learn how to use the feature by taking a look at the getting started guide.

For more context, see the related issue in Meilisearch: https://github.com/meilisearch/meilisearch/issues/5713

NB: the chat API was released in Meilisearch 1.15.1.

Tasks

• [ ] Add the new methods to interact with the Meilisearch API
• [ ] Add new tests cases