Update dataset card metadata and link to paper/GitHub

This PR updates the dataset card:
- Moves the arXiv ID from the YAML metadata to the Markdown section as a paper link, per Hugging Face guidelines.
- Adds `task_categories: [other]` to the metadata.
- Links to the official GitHub repository for code and annotated pairs.

README.md

@@ -1,6 +1,13 @@
 ---
 license: apache-2.0
-arxiv: 2605.15868
+task_categories:
+- other
 ---
 
-sym-MM2MM is the benchmark of paper "SOLAR: Self-supervised Joint Learning for Symmetric Multimodal Retrieval". This repository contains the candidate pool of 1M LAION pairs. For annotated pairs, please refer to <https://github.com/codefuse-ai/SOLAR>.
+# sym-MM2MM
+
+sym-MM2MM is the benchmark dataset for the paper [SOLAR: Self-supervised Joint Learning for Symmetric Multimodal Retrieval](https://huggingface.co/papers/2605.15868).
+
+This repository contains the candidate pool of 1M LAION pairs. 
+
+For annotated pairs and code, please refer to the [GitHub Repository](https://github.com/codefuse-ai/SOLAR).