Update README.md

Hi there! First of all, I want to say that your model is fantastic. We would love to contribute by updating the README to include the base_model information. This will help address the missing model card details. Thank you!

README.md

@@ -1,5 +1,7 @@
 ---
 license: mit
+base_model:
+- openai-community/gpt2
 ---
 
 # MagicPrompt - Stable Diffusion