Add `language_bcp47` tag (#4753)

* fix ms_terms

* fix ted_talks_iwslt

* move tags to language_bcp47

* fix bad codes

* add language_details and language_bcp47 in DatasetMetadata

* more fixes

* fix wiki_dpr

Commit from https://github.com/huggingface/datasets/commit/aa48a29d1304167dff37cef0ed7542f29376ee2d

README.md

@@ -5,7 +5,8 @@ language_creators:
 - found
 language:
 - ro
-- ro-md
+language_bcp47:
+- ro-MD
 license:
 - cc-by-4.0
 multilinguality: