[i18n] Update frontend/ui/language: add Basque and uncomment Vietnamese (#3755)

Adds Basque (new) and uncomments Vietnamese (now partially translated).

Fixes #3749.

frontend/ui/language.lua

@@ -39,6 +39,7 @@ function Language:getLangMenuTable()
                 self:genLanguageSubItem("Čeština", "cs_CZ"),
                 self:genLanguageSubItem("Deutsch", "de"),
                 self:genLanguageSubItem("Español", "es"),
+                self:genLanguageSubItem("Euskara", "eu"),
                 self:genLanguageSubItem("Français", "fr"),
                 self:genLanguageSubItem("Galego", "gl"),
                 self:genLanguageSubItem("Italiano", "it_IT"),
@@ -50,7 +51,7 @@ function Language:getLangMenuTable()
                 self:genLanguageSubItem("Português", "pt_PT"),
                 self:genLanguageSubItem("Português do Brasil", "pt_BR"),
                 self:genLanguageSubItem("Svenska", "sv"),
-                --self:genLanguageSubItem("Tiếng Việt", "vi"),
+                self:genLanguageSubItem("Tiếng Việt", "vi"),
                 self:genLanguageSubItem("Türkçe", "tr"),
                 --self:genLanguageSubItem("Viet Nam", "vi_VN"),
                 --self:genLanguageSubItem("عربى", "ar_AA"),