Add Crimean Tatar as available content language

[witchmonster]

Add a two-letter code to Crimean Tatar language, so it shows up in the list.
There's a large Crimean Tatar community asking this for quite a while.

Note: "ct" for "Crimean Tatar" is not an official ISO_639-1 standard
However, this language code is unassigned in ISO_639-1, so it can be used safely without conflicts with existing codes:

Please support indeginous people of Crimea during this horrible time of Russian occupation. They have experienced multiple ethnic cleansings and are fighting for their language and culture every day in occupation or exile.

There's also a large Crimean Tatar community on Bluesky asking for this change:
https://bsky.app/profile/mathan.dev/post/3jzwxyx2gpw2g

We need this to build feeds and discovery for new Crimean Tatar users, joining the platform.

[pfrazee]

Let's find a more robust solution for this. Introducing a new 2-letter code is likely to cause confusion; since there is a valid 3-letter code, we should use that and ensure it shows up in the available languages.

To do this, we should make some improvements to the codebase. It was originally built around the 2-letter codes (ie the preference stored uses the 2-letter) and we just need to add 3-letter support. The bcp-47-match library can help us transition the code. We can then update the UI to list the missing items.

[witchmonster]

Thank you, Paul!

I've seen that there's a code-2 filtration on the list of languages and that causes for Crimean Tatar (which does not have one) to not show up in the list, so that would be just a "quick fix".

But I fully agree, that your solution on shifting the focus on 3-letter codes would be a much better fit than a hack with using an unassigned ISO_639-1.

Thank you for considering this. Our community will be very grateful for the change!