Update library name to vLLM

It seems the model is not Transformers compatible, but vLLM compatible. Hence this PR updates the `library_name` to vLLM.

README.md

@@ -1,6 +1,6 @@
 ---
 license: mit
-library_name: transformers
+library_name: vllm
 pipeline_tag: image-text-to-text
 ---