Fix C++ 17 support

src/languages/index.ts

@@ -32,6 +32,7 @@ export const languages: Language[] = [
     require('./c'),
     require('./cpp'),
     require('./cpp11'),
+    require('./cpp17'),
     require('./csharp'),
     require('./haskell'),
     require('./java'),
@@ -49,4 +50,4 @@ export const languages: Language[] = [
 
 export function getLanguage(name: string): Language {
     return name == null ? null : languages.find(l => l.name === name);
-}
+}