Align more metadata with other repo types (models,spaces) (#4607)
Browse files* 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 <[email protected]>
Commit from https://github.com/huggingface/datasets/commit/a5192964dc4b76ee5c03593c11ee56f29bbd688d