Add `lang` tag to native language names in language picker (#23749)

app/javascript/mastodon/features/compose/components/language_dropdown.js

@@ -216,7 +216,7 @@ class LanguageDropdownMenu extends React.PureComponent {
 
     return (
       <div key={lang[0]} role='option' tabIndex='0' data-index={lang[0]} className={classNames('language-dropdown__dropdown__results__item', { active: lang[0] === value })} aria-selected={lang[0] === value} onClick={this.handleClick} onKeyDown={this.handleKeyDown}>
-        <span className='language-dropdown__dropdown__results__item__native-name'>{lang[2]}</span> <span className='language-dropdown__dropdown__results__item__common-name'>({lang[1]})</span>
+        <span className='language-dropdown__dropdown__results__item__native-name' lang={lang[0]}>{lang[2]}</span> <span className='language-dropdown__dropdown__results__item__common-name'>({lang[1]})</span>
       </div>
     );
   }