feat: Add chat template

tokenizer_config.json

@@ -319,5 +319,6 @@
   "eos_token": "<|endoftext|>",
   "model_max_length": 2048,
   "tokenizer_class": "CodeGenTokenizer",
-  "unk_token": "<|endoftext|>"
+  "unk_token": "<|endoftext|>",
+  "chat_template": "{{ if .System }}System: {{ .System }} {{ end }}User: {{ .Prompt }} Assistant:"
 }