Subpages does not detect/redirect to userLang page

[design-rrr]

Current behaviour
https://bitcoin-safe.org/news/ goes to GH default 404 page

Expected behaviour
https://bitcoin-safe.org/news/ should redirect to

• https://bitcoin-safe.org/en/news/ when en_XX is the detected language
• https://bitcoin-safe.org/es/news/ when es_XX is the detected language
• etc...