add `library_name=transformers` tag for deploy button to display

https://discuss.huggingface.co/t/deploy-button-not-showing-fine-tuned-llama-3-1/103630/2

README.md

@@ -1,5 +1,7 @@
 ---
 license: apache-2.0
+pipeline_tag: text-generation
+library_name: transformers
 ---
 # Reka Flash 3