Add catalan strings

[vmadalin]

Description

Add support for the Catalan language as it was requested in #462

[alorma]

As i'm not an expert, some comments

[vmadalin]

Thanks to @franzeszpere, @javichaques and @alorma for your contribution helping this project to improve Catalan translations PR. I applied all of your suggestions :), please check if all are ok now.

[alorma]

@vmadalin

Let me ping @Ereza as he knows better than me about Catalan translations

[Ereza]

There are several issues, I added suggestions for everything I think could be improved. The most common issue is that in Catalan, actions in buttons or menus must always be in imperative tense, not in infinitive (other languages like Spanish use infinitives instead, so this is a common error). For example, "Afegir" should be "Afegeix".

Oh, and thanks for translating it into Catalan! :P

[googlebot]

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[Ereza]

@googlebot I fixed it.

[googlebot]

CLAs look good, thanks!

ℹ️ Googlers: Go here for more info.

[vmadalin]

@Ereza Thank you numerous contribution to improve Catalan translation for this sample project, I merge several of them having pending only two suggest changes to discuss more in detail.

[vmadalin]

@Ereza Thanks again for your contribution and time reviewing the translations 👏 . I update the PR with all the suggestions. Please review them and let's approve it for merge. Thank you all

[Ereza]

Looks great, thanks for your time! :)

[tiembo]

Thank you everyone for contributing to this translation! Added this to the list of translations on the Wiki.