Align more metadata with other repo types (models,spaces) (#4607)

* language(s) and license(s) for consistency

* `licenses:` => `license:`

* `languages:` => `language:`

* backward-compat

* make style

* set default values for deprecated languages and licenses

Co-authored-by: Quentin Lhoest <lhoest.q@gmail.com>

Commit from https://github.com/huggingface/datasets/commit/a5192964dc4b76ee5c03593c11ee56f29bbd688d

README.md

@@ -3,7 +3,7 @@ annotations_creators:
 - expert-generated
 language_creators:
 - crowdsourced
-languages:
+language:
 - bn
 - en
 - fil
@@ -17,7 +17,7 @@ languages:
 - th
 - vi
 - zh
-licenses:
+license:
 - cc-by-4.0
 multilinguality:
 - multilingual
@@ -89,7 +89,7 @@ Machine Translation, Dependency Parsing
 
 ### Languages
 
-It supports 13 languages: 
+It supports 13 language: 
   * Bengali
   * English
   * Filipino