Those are fields used by the language switcher to correlate pages across
different languages, even if they have different names/paths/titles.
They are generated with the prepare_for_translation.py script.
- mark all code blocks with ```
- unify empty lines between sections
- adjust list syntax (no space before dash)
- adjust headers to use Atx-style syntax
- remove trailing spaces
- Moves the "Qubes RPC internals" section to qrexec-internals.md.
- Fixes redirects for new pages.
- Retitles docs to reflect deprecation of qrexec2.
- Revises the texts and links referring to deprecated qrexec2 docs.
