Added Vietnamese Docs/readme translation.
Added links to the Vietnamese Docs/readme in the other Docs/readme translations.
Added Vietnamese Privacy Policy translation.
Added Vietnamese FAQ translation.
Added links to the Vietnamese FAQ in the other FAQ translations.
Added Vietnamese SECURITY-FAQ translation.
Added links to the Vietnamese FAQ in the other SECURITY-FAQ translations.
Added placeholder for Vietnamese Guide__Installing translation.
Added placeholder for Vietnamese Guide__Troubleshooting translation.
Fixed typos.
Khang