[docs] Ukrainian translation

[matrunchyk]

What problem is this solving

Hi! We are the Ukrainian VueJS documentation translation team. We have localized ua.vuejs.org, vue3-migration guide and are now completed the pinia documentation translation to Ukrainian.

Here is our translation status: vuejs-ua#5

Proposed solution

We would like to create a PR to merge into the upstream (this repo). Other translations are not overridden, we worked in a specific directory, followed the same approach as for already other existing translations.

Upd: Wow, issue number 2222, this is a sign! 😆