Update README.md

The InternLM2 model is truly impressive! We would like to contribute by updating the README to include the base_model information. This will help address the current gap in the model card.

README.md

@@ -1,6 +1,8 @@
 ---
 pipeline_tag: text-generation
 license: other
+base_model:
+- internlm/internlm2-base-7b
 ---
 # InternLM