Show completion % for translations

[solonovamax]

Currently, some translations are incomplete. Currently, es, it, kr, pl, rs, ru, and ua are incomplete.

The website should include a completion % for how much languages have been completed, as well as a "contribute to the translations" button.

[oetherington]

If any one wants to take this on, the data is available in the "translation-report" stage of the CI for every pushed commit (for instance, https://github.com/Ukraine-Relief-Efforts/ukraine-info-guide/runs/5577228914?check_suite_focus=true).

However, I think getting this into a format that we can easily show on the site is non-trivial. For now, it might suffice to just add some text to the "about us" page saying that translations can be submitted on Github.