Update wiki docs about our website development workflow in accordance with the GitLab CI migration
As discussed in the Community Team meeting today, we need to update the wiki pages, for instance:
https://gitlab.torproject.org/tpo/web/wiki/-/wikis/Compiling-a-local-version-of-the-website
https://gitlab.torproject.org/tpo/web/wiki/-/wikis/How-to-enable-a-new-locale
We also need to review (and update) the docs at other places:
https://gitlab.torproject.org/tpo/web/tpo/-/blob/main/CONTRIBUTING.md
https://gitlab.torproject.org/tpo/web/tpo/-/blob/main/README.md
https://gitlab.torproject.org/tpo/web/community/-/blob/main/README.md