[i18n-vi] Translate README.md to Vietnamese (#29229)

* Add Tiếng Việt language support

* Add Vietnamese translation link to README.md

* update README_vi.md

README_ja.md

@@ -87,6 +87,7 @@ user: ユーザ
         <a href="https://github.com/huggingface/transformers/blob/main/README_te.md">తెలుగు</a> |
         <a href="https://github.com/huggingface/transformers/blob/main/README_fr.md">Français</a> |
         <a href="https://github.com/huggingface/transformers/blob/main/README_de.md">Deutsch</a> |
+        <a href="https://github.com/huggingface/transformers/blob/main/README_vi.md">Tiếng Việt</a> |
     </p>
 </h4>