Add library name

This PR improves the model card by adding a `library_name` tag, which lets users know that this model is compatible with the `transformers` library and can hence be used like `from transformers import AutoModelForCausalLM`.

README.md

@@ -1,6 +1,7 @@
 ---
 license: apache-2.0
 pipeline_tag: text-generation
+library_name: transformers
 ---
 
 # 🧨 FLAME-MoE