Add task category, paper link, and dataset description

This PR adds the `image-segmentation` task category, a link to the paper, and a short description of the dataset purpose to the dataset card.

README.md

@@ -30,4 +30,10 @@ configs:
     path: data/train-*
   - split: validation
     path: data/validation-*
+task_categories:
+- image-segmentation
 ---
+
+This dataset is used for training and evaluating conditional image generation models, as described in the paper [Ctrl-U: Robust Conditional Image Generation via Uncertainty-aware Reward Modeling](https://huggingface.co/papers/2410.11236).
+
+Project page: https://grenoble-zhang.github.io/Ctrl-U-Page/