add directive for code blocks to stay in LTR even when in RTL text. part of...

add directive for code blocks (also embedded) to stay in LTR even when in RTL text. will-fix: tpo/community/l10n#40120 (closed)

see the difference between https://review.torproject.net/tpo/web/support/review-l10n-40120-01iaw7/ar/get-in-touch/why-i-cant-join-tor-channels/ and https://support.torproject.org/ar/get-in-touch/why-i-cant-join-tor-channels/ on the commands.