"This Page Is Not Yet Translated"

Courtesy of @smikitky

It would be cool to have a "This Page Is Not Yet Translated" component that we can stick on pages in the translation forks that haven't had a translation yet. Even though the Spanish translation is "done", some sections like the blog aren't translated, and it would be nice to give a warning like MDN does:

This would involve something like:

• A TranslationWarning component with a message on how a page isn't translated yet.
• A translated property on front matter that should be set when a page is translated
• Logic to show the translation warning if translated isn't set (and the language isn't English).

This would require a code mod for all the pages that have been already translated in the various languages, but I could probably do that with a codemod by referencing their progress list.

Start by locating the proposed TranslationWarning component, the translated front-matter property, and the language-based display logic described in the issue. Review the existing translated pages and language progress lists before planning the codemod; done means untranslated non-English pages show the warning while translated pages and English pages do not.