Add evaluation results on the squad_v2 config of squad_v2

Beep boop, I am a bot from Hugging Face's automatic model evaluator 👋!\
Your model has been evaluated on the squad_v2 config of the [squad_v2](https://huggingface.co/datasets/squad_v2) dataset by

@nbroad

, using the predictions stored [here](https://huggingface.co/datasets/autoevaluate/autoeval-eval-project-squad_v2-1e2c143e-1305549899).\
Accept this pull request to see the results displayed on the [Hub leaderboard](https://huggingface.co/spaces/autoevaluate/leaderboards?dataset=squad_v2).\
Evaluate your model on more datasets [here](https://huggingface.co/spaces/autoevaluate/model-evaluator?dataset=squad_v2).

README.md

@@ -22,6 +22,23 @@ model-index:
       type: f1
       value: 55.135
       verified: true
+  - task:
+      type: question-answering
+      name: Question Answering
+    dataset:
+      name: squad_v2
+      type: squad_v2
+      config: squad_v2
+      split: validation
+    metrics:
+    - name: Exact Match
+      type: exact_match
+      value: 79.2432
+      verified: true
+    - name: F1
+      type: f1
+      value: 82.336
+      verified: true
 task:
 - question-answering
 datasets: