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

@lewtun

, using the predictions stored [here](https://huggingface.co/datasets/autoevaluate/autoeval-staging-eval-project-squad_v2-7c1a5e5f-11505530).\
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

@@ -3,6 +3,30 @@ language: en
 datasets:
 - squad_v2
 license: cc-by-4.0
+model-index:
+- name: autoevaluate/roberta-base-squad2
+  results:
+  - 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: 79.9326
+      verified: true
+    - name: F1
+      type: f1
+      value: 82.9488
+      verified: true
+    - name: total
+      type: total
+      value: 11870
+      verified: true
 ---
 
 # roberta-base for QA