Add prompt format hint

correct format according to reddit:

https://www.reddit.com/r/LocalLLaMA/comments/18ckls0/mambachat_a_chat_llm_based_on_state_space_models/

README.md

@@ -6,4 +6,13 @@ Mamba-Chat is the first chat language model based on a state-space model archite
 
 The model is a fine-tune of Albert Gu's and Tri Dao's model [Mamba-2.8B](https://github.com/state-spaces/mamba) from their paper *Mamba: Linear-Time Sequence Modeling with Selective State Spaces*.
 
-Check our our [Github repository](https://github.com/havenhq/mamba-chat/tree/main) for training and inference code.
+Check our our [Github repository](https://github.com/havenhq/mamba-chat/tree/main) for training and inference code.
+
+The prompt format is the zephyr format:
+
+```
+<|user|> {user_message}
+<|assistant|> {assistant_message}
+<|user|> {user_message}
+<|assistant|> {assistant_message}
+```