What does it take to add a langue to Duolingo? Cajun french is a rapidly dying langue. I think it would be great to see a revival of this unique french dialect.
It's worth looking in the help section of the website for these sorts of questions. There's a link at the bottom of every Duolingo page, and in the menu that appears when you hold your mouse over the username at the top of the page.
Have a look at this article from the help section: https://support.duolingo.com/hc/en-us/articles/204979660-How-can-I-suggest-a-new-language-course-
By an amazing coincidence I was just reading about Cajun French (and Patwa) earlier today. I agree that it would be great if it, along with hundreds of other dying languages, could be revived. But would it be the best use of Duolingo's staff's time to develop such a course, even assuming people able to do so were at hand? I mean, how many people would actually be interested in doing such a course?