Add Catalan (Valencia)

@nedbat Added this because the requester for the language said, when I asked if "Catalan" would be ok:

"Both languages share the same origin but they are quite different and are regulated by different academies of language. In some way is like spanish spoken in Spain and the one spoken Latin America.

I'm from a valencian university and here we have a languages area that could perform the valencian translation but we are not sure we have sufficient skills to do the catalan one."