Add model card

This PR adds a model card by linking it to the paper [Flowing from Words to Pixels: A Framework for Cross-Modality Evolution](https://huggingface.co/papers/2412.15213).

It also adds a relevant pipeline tag, and link to the Github repository.

Please review and merge this PR if everything looks good.

README.md

@@ -1,3 +1,10 @@
----
-license: mit
----
+---
+license: mit
+library_name: diffusers
+pipeline_tag: text-to-image
+---
+
+This repository contains the model described in the paper [Flowing from Words to Pixels: A Framework for Cross-Modality Evolution](https://huggingface.co/papers/2412.15213).
+
+Code: https://github.com/qihao067/CrossFlow.
+```