What can I do for CI4?

My name is Toni, I'm from Spain, I've been programming in PHP for a few years and I'd like to contribute with CI4, so far I've done 2 pull requests of little things on github.

I had thought to do as there is credit card validator the same for bank accounts (IBAN), I don't know if it go in the line of CI4, before doing so I opened this topic. 

If you can guide me in what ways I can collaborate, I would be grateful.

PD: I speak spanish, Would it be nice to make a translation of the Language/en/* directory into Spanish?

The best.