First export with https://gerrit.wikimedia.org/r/c/mediawiki/core/+/1033888

• Verify autonym correctness in language-data
• Add to includes/languages/data/Names.php
• Add to RELEASE-NOTES
• Set fallback if needed
  • In core (languages/messages/Messages*.php)
  • In jquery.i18n (src/jquery.i18n.fallbacks.js)
  • Remove fallback gender aliases if needed
• Add namespace translations
  • Add gender aliases if needed
  • Check that namespace translations don't conflict with language codes
• Add $linkTrail
• Add date formats (if needed)
• Add digit conversion (if needed)
• Define wider line-height in resources/src/mediawiki.skinning/i18n-headings.less (if needed)
• Remove from translatewiki after deploying the core change
  • mw-config/LanguageSettings.php
  • mw-config/FallbackSettings.php
• Test language search in UniversalLanguageSelector and fix the search index if needed