pepoliveras
Catalan language is available on Weblate: https://weblate.rob006.net/languages/ca/flarum/ - you should have language pack maintainer permission there.
I created repository for Catalan language pack: https://github.com/flarum-lang/catalan - I've sent you invite, you should have maintainer permissions there as soon ans you accept it. Composer package should be registered tomorrow.
You can already start translating on Weblate. Translations from Weblate will be exported to GitHub repository after ~1 hour. You will be able to test it using composer require flarum-lang/catalan:dev-master
command to install it. When you will be ready to tag stable release, you can approve this PR: flarum-lang/catalan1. Just remember to approve PR instead of merging it (there are instructions in first comment in this PR).