feat!: add function calling support to client.chat() & client.chat_async()

BREAKING CHANGE: Too many to count in this version. Check the README examples.

src/v1/mod.rs

@@ -1,7 +1,10 @@
-pub mod chat_completion;
+pub mod chat;
+pub mod chat_stream;
 pub mod client;
 pub mod common;
 pub mod constants;
 pub mod embedding;
 pub mod error;
 pub mod model_list;
+pub mod tool;
+pub mod utils;