Mark missing translation for duplicated content

[lianmakesthings]

When English content is duplicated to other languages, it may lead to confusion for the reader. They may think we are delivering the wrong page, for example.
At the moment, we are asking the PR authors to add a note in English to the duplicated website, but it's not always done.

One way to solve this could be to e.g. add a note in French that this page has been duplicated from the English page and not translated yet, automatically.

[lianmakesthings]

We could also solve this trough tagging content with "missing translation"