Add base model

This PR ensures the model is shown as a fine-tune of https://huggingface.co/llava-hf/llava-1.5-7b-hf.

README.md

@@ -1,4 +1,5 @@
 ---
+base_model: llava-hf/llava-1.5-7b-hf
 library_name: transformers
 pipeline_tag: image-text-to-text
 tags: []