add chat prompt template

tokenizer_config.json

@@ -38,5 +38,6 @@
   "spaces_between_special_tokens": false,
   "tokenizer_class": "LlamaTokenizer",
   "unk_token": "<unk>",
+  "chat_template": "{% for message in messages %}{% if message['role'] == 'user' %}{{ '\n\nHuman: ' + message['content']}}{% elif message['role'] == 'assistant' %}{{ '\n\nAssistant: ' + message['content'] + eos_token}}{% else %}{{ raise_exception('Only user and assistant roles are supported!') }}{% endif %}{% if loop.last and add_generation_prompt %}{{ '\n\nAssistant: ' }}{% endif %}{% endfor %}",
   "use_default_system_prompt": false
 }