Russian translation of PRIMER Phase 1

[novy4]

I spent more than 5 hours to translate phase 1 docs to the Russian language, please accept my PR.

[RiccardoM]

@novy4 I've pulled the master branch into your PR to make sure everything was up-to-date.

I've also changed how the translated files are arranged to match Vuepress i18n config.

Finally I've added a .vuepress/config_ru.js file that configures the translated version of the documentation. I'd like you to go over that file and translate only the things that I've marked with //TODO.

Again, thank you so much for the service you provided 🙏

One last thing: the next time, please, do not translate what comes next to :::. this is a Vuepress Markdown extension that, if translated, does not work anymore.

Thank you so much. Waiting for your last translations to merge this 🚀