Adding eval metadata for arabic speech corpus (#4332)

* Adding eval metadata for arabic speech corpus

Adding eval metadata for arabic speech corpus

* Update README.md

fixing unicode error

Commit from https://github.com/huggingface/datasets/commit/dffb95f9a6b17e48d5171c7c3d377ee8f9e4919e

README.md

@@ -18,6 +18,21 @@ source_datasets:
 task_categories:
 - automatic-speech-recognition
 task_ids: []
+train-eval-index:
+- config: clean
+  task: automatic-speech-recognition
+  task_id: speech_recognition
+  splits:
+    train_split: train
+    eval_split: test
+  col_mapping:
+    file: path
+    text: text
+  metrics:
+  - type: wer
+    name: WER
+  - type: cer
+    name: CER
 ---
 
 # Dataset Card for Arabic Speech Corpus