Docs: Indicate links in foreign language in Translations page (#40767)

Co-authored-by: Julien Déramond <[email protected]>
Co-authored-by: Patrick H. Lauke <[email protected]>

site/content/docs/5.3/about/translations.md

@@ -10,7 +10,7 @@ Community members have translated Bootstrap's documentation into various languag
 {{< translations.inline >}}
 <ul>
 {{ range .Site.Data.translations -}}
-  <li><a href="{{ .url }}" hreflang="{{ .code }}">{{ .description }} ({{ .name }})</a></li>
+  <li><a href="{{ .url }}" hreflang="{{ .code }}" lang="{{ .code }}">{{ .description }} ({{ .name }})</a></li>
 {{ end -}}
 </ul>
 {{< /translations.inline >}}