- Introducues generate_content_stream that returns a Tokio Steam instead
of a Queue. This allows using the standard stream APIs from
tokio-streams.
- Replace future-utils with tokio-streams, mainly due to better
ergonomics for using the filter_map stream combinator.
- Add base code for the Vertex API with types and a client with helper
methods for prompting text and conversation.
- Add examples for prompting text and conversation.
