Bring navigation link labels to non-English languages

[das-g]

Issue description

PR #1495 brought text labels to the prev/next links and to the top menu icons (ToS toggle, language switcher, and font settings menu), but it did so only for the English version.

We should make this available in the translated versions as well.

Language

all except English

[das-g]

I'm not sure how to proceed with this, as the new CSS file doesn't show up on Crowdin, yet.

We could:

• use the English labels untranslated
  • by copying the unchanged file to every language
    or maybe
  • by moving it to the top-level directory (repository root)
• translate the labels outside of Crowdin
• see whether we can change the Crowdin configuration, so that this file can be translated there