Add support of Fon language (no supported in libicu)

src/tools/languageTools.cpp

@@ -22,6 +22,7 @@ std::map<std::string, std::string> iso639_3 = {
     {"dty", "डोटेली"},
     {"eml", "emiliân-rumagnōl"},
     {"fbs", "српскохрватски"},
+    {"fon", "fɔ̀ngbè"},
     {"guw", "Gungbe"},
     {"hbs", "srpskohrvatski"},
     {"ido", "ido"},
@@ -71,4 +72,4 @@ std::string getLanguageSelfName(const std::string& lang)
     return lang;
 };
 
-} // namespace kiwix
+} // namespace kiwix