Improve model card: add robotics pipeline tag, library name, and project page link

This PR improves the model card for the paper [WorldVLA: Towards Autoregressive Action World Model](https://huggingface.co/papers/2506.21539) by:
- Adding the `robotics` pipeline tag.
- Adding the `transformers` library name.
- Adding a link to the project page.

README.md

@@ -1,3 +1,9 @@
----
-license: apache-2.0
----
+---
+license: apache-2.0
+pipeline_tag: robotics
+library_name: transformers
+---
+
+This repository contains the model presented in the paper [WorldVLA: Towards Autoregressive Action World Model](https://huggingface.co/papers/2506.21539).
+
+Project page: https://github.com/alibaba-damo-academy/WorldVLA