Declare base_model: microsoft/deberta-xlarge-mnli

The card prose already states this model is fine-tuned from microsoft/deberta-xlarge-mnli, but the metadata did not, so Hugging Face excluded it from that base model's fine-tune graph. Search Console shows the base model name is what people actually search: the one sibling model that does declare base_model is this account's highest-traffic page.

README.md

@@ -1,4 +1,5 @@
 ---
+base_model: microsoft/deberta-xlarge-mnli
 license: mit
 datasets:
 - dair-ai/emotion