Improve model card with pipeline tag and library name

This PR improves the model card by adding the `pipeline_tag` and `library_name` metadata, enhancing the model's discoverability on the Hugging Face Hub. The `pipeline_tag` is set to `text-to-3d` to accurately reflect the model's functionality, and `library_name` is set to `diffusers` given the model's reliance on diffusion model technology.

README.md

@@ -1,5 +1,7 @@
 ---
 license: apache-2.0
+pipeline_tag: text-to-3d
+library_name: diffusers
 ---
 
 # Kiss3DGen