Add task_categories and size_categories to yaml

Added task_categories and size_categories to the yaml so the dataset shows up in Hub task and size filters. No other changes.

README.md

@@ -26,6 +26,10 @@ configs:
 license: cc-by-nc-4.0
 language:
 - en
+task_categories:
+- text-to-speech
+size_categories:
+- 10K<n<100K
 pretty_name: The Expresso Dataset
 ---