Built-in extension: informing about translation progress

Is your feature request related to a problem? Please describe.
Sphinx projects which are being translated into multiple languages using Gettext, when a translation is still in progress, display original paragraphs as a fallback to missing translations of paragraphs. That could be unexpected for a reader looking at a project in some language (which for example can be translated in a majority of content).

Describe the solution you'd like
Built-in extension to enable displaying a note paragraph at the top of every article that is not fully translated, informing a reader about the progress of the translation in the article.

Would such an extension be accepted as a built-in?

Describe alternatives you've considered

• third party extension – in my opinion the described functionality being accessible as batteries-included inside Sphinx would be beneficial to many projects around, as publishing the in progress translations seems to be a quite common case for projects using intl

Additional context

• https://github.com/python/docsbuild-scripts/issues/148
• related/ground work
  • https://github.com/sphinx-doc/sphinx/issues/11157 (https://github.com/sphinx-doc/sphinx/pull/11502)
  • https://github.com/sphinx-doc/sphinx/pull/11509

Start with Sphinx's Gettext internationalization documentation and the related issue #11157 and pull requests #11502 and #11509. Determine how a built-in extension should detect an incompletely translated article and expose the note behavior requested here. Done means an accepted design and implementation that informs readers at the top of every article whose translation is incomplete.