Added Listing to Term.

So far only added to English.

data/translations/en.yaml

@@ -19,3 +19,4 @@ See: see
 SeeAlso: see also
 Table: Table
 To: To
+Listing: Listing

src/Text/Pandoc/Translations.hs

@@ -76,6 +76,7 @@ data Term =
   | To
   | Proof
   | Glossary
+  | Listing
   deriving (Show, Eq, Ord, Generic, Enum, Read)
 
 newtype Translations = Translations (M.Map Term String)