Add pipeline tag: feature-extraction

This PR improves the model card by adding the `pipeline_tag: feature-extraction` to the metadata. This will help users discover the model when searching for feature extraction models on the Hugging Face Hub, as the model learns unified semantic embeddings of brain signals.

README.md

@@ -1,6 +1,8 @@
 ---
 license: mit
+pipeline_tag: feature-extraction
 ---
+
 # BrainOmni 🧠
 
 <div align="center">
@@ -37,4 +39,4 @@ If you use BrainOmni model or code, please cite the following paper:
 
 > Qinfan Xiao, Ziyun Cui, Chi Zhang, Siqi Chen, Wen Wu, Andrew Thwaites, Alexandra Woolgar,
 Bowen Zhou, Chao Zhang (2025) BrainOmni: A Brain Foundation Model for Unified EEG and MEG Signals,
-_arXiv_, [https://arxiv.org/abs/2505.18185](https://arxiv.org/abs/2505.18185)
+_arXiv_, [https://arxiv.org/abs/2505.18185](https://arxiv.org/abs/2505.18185)