[Model] Initialize support for InternVL2 series models (#6514)

Co-authored-by: Roger Wang <ywang@roblox.com>

vllm/entrypoints/chat_utils.py

@@ -107,7 +107,7 @@ def _image_token_str(model_config: ModelConfig,
         return None
     if model_type.startswith("llava"):
         return tokenizer.decode(model_config.hf_config.image_token_index)
-    if model_type == "chameleon":
+    if model_type in ("chameleon", "internvl_chat"):
         return "<image>"
     raise TypeError(f"Unknown model type: {model_type}")