Add Vietnamese Translation (#684)

library/src/layout/table.rs

@@ -298,6 +298,7 @@ impl LocalName for TableElem {
             Lang::SLOVENIAN => "Tabela",
             Lang::SPANISH => "Tabla",
             Lang::UKRAINIAN => "Таблиця",
+            Lang::VIETNAMESE => "Bảng",
             Lang::ENGLISH | _ => "Table",
         }
     }

library/src/math/mod.rs

@@ -286,6 +286,7 @@ impl LocalName for EquationElem {
             Lang::SLOVENIAN => "Enačba",
             Lang::SPANISH => "Ecuación",
             Lang::UKRAINIAN => "Рівняння",
+            Lang::VIETNAMESE => "Phương trình",
             Lang::ENGLISH | _ => "Equation",
         }
     }

library/src/meta/bibliography.rs

@@ -213,6 +213,7 @@ impl LocalName for BibliographyElem {
             Lang::SLOVENIAN => "Literatura",
             Lang::SPANISH => "Bibliografía",
             Lang::UKRAINIAN => "Бібліографія",
+            Lang::VIETNAMESE => "Tài liệu tham khảo",
             Lang::ENGLISH | _ => "Bibliography",
         }
     }

library/src/meta/heading.rs

@@ -241,6 +241,7 @@ impl LocalName for HeadingElem {
             Lang::SLOVENIAN => "Poglavje",
             Lang::SPANISH => "Sección",
             Lang::UKRAINIAN => "Розділ",
+            Lang::VIETNAMESE => "Phần", // TODO: This may be wrong.
             Lang::ENGLISH | _ => "Section",
         }
     }

library/src/meta/outline.rs

@@ -264,6 +264,7 @@ impl LocalName for OutlineElem {
             Lang::SLOVENIAN => "Kazalo",
             Lang::SPANISH => "Índice",
             Lang::UKRAINIAN => "Зміст",
+            Lang::VIETNAMESE => "Mục lục",
             Lang::ENGLISH | _ => "Contents",
         }
     }

library/src/text/raw.rs

@@ -212,6 +212,7 @@ impl LocalName for RawElem {
             Lang::RUSSIAN => "Листинг",
             Lang::SLOVENIAN => "Program",
             Lang::UKRAINIAN => "Лістинг",
+            Lang::VIETNAMESE => "Chương trình", // TODO: This may be wrong.
             Lang::ENGLISH | _ => "Listing",
         }
     }

library/src/visualize/image.rs

@@ -130,6 +130,7 @@ impl LocalName for ImageElem {
             Lang::SLOVENIAN => "Slika",
             Lang::SPANISH => "Figura",
             Lang::UKRAINIAN => "Рисунок",
+            Lang::VIETNAMESE => "Hình",
             Lang::ENGLISH | _ => "Figure",
         }
     }

src/doc.rs

@@ -528,6 +528,7 @@ impl Lang {
     pub const SLOVENIAN: Self = Self(*b"sl ", 2);
     pub const SPANISH: Self = Self(*b"es ", 2);
     pub const UKRAINIAN: Self = Self(*b"ua ", 2);
+    pub const VIETNAMESE: Self = Self(*b"vi ", 2);
 
     /// Return the language code as an all lowercase string slice.
     pub fn as_str(&self) -> &str {