Add prompts templates to a markdown doc (#489)

* Add prompts templates to a markdown doc

* rm line about mistral

PROMPTS.md

@@ -0,0 +1,27 @@
+# Prompt templates
+
+These are the templates used to format the conversation history for different models used in HuggingChat. Set them in your `.env.local` [like so](https://github.com/huggingface/chat-ui#chatprompttemplate).
+
+## Llama 2
+
+```env
+<s>[INST] <<SYS>>\n{{preprompt}}\n<</SYS>>\n\n{{#each messages}}{{#ifUser}}{{content}} [/INST] {{/ifUser}}{{#ifAssistant}}{{content}} </s><s>[INST] {{/ifAssistant}}{{/each}}
+```
+
+## CodeLlama
+
+```env
+<s>[INST] <<SYS>>\n{{preprompt}}\n<</SYS>>\n\n{{#each messages}}{{#ifUser}}{{content}} [/INST] {{/ifUser}}{{#ifAssistant}}{{content}} </s><s>[INST] {{/ifAssistant}}{{/each}}
+```
+
+## Falcon
+
+```env
+System: {{preprompt}}\nUser:{{#each messages}}{{#ifUser}}{{content}}\nFalcon:{{/ifUser}}{{#ifAssistant}}{{content}}\nUser:{{/ifAssistant}}{{/each}}
+```
+
+## Mistral
+
+```env
+<s>{{#each messages}}{{#ifUser}}[INST] {{#if @first}}{{#if @root.preprompt}}{{@root.preprompt}}\n{{/if}}{{/if}} {{content}} [/INST]{{/ifUser}}{{#ifAssistant}}{{content}}</s> {{/ifAssistant}}{{/each}}
+```

README.md

@@ -183,7 +183,7 @@ For example:
 
 When quering the model for a chat response, the `chatPromptTemplate` template is used. `messages` is an array of chat messages, it has the format `[{ content: string }, ...]`. To idenify if a message is a user message or an assistant message the `ifUser` and `ifAssistant` block helpers can be used.
 
-The following is the default `chatPromptTemplate`, although newlines and indentiation have been added for readability.
+The following is the default `chatPromptTemplate`, although newlines and indentiation have been added for readability. You can find the prompts used in production for HuggingChat [here](https://github.com/huggingface/chat-ui/blob/main/PROMPTS.md).
 
 ```prompt
 {{preprompt}}