Fix cz=>cs iso lang code for Czech translation

app/src/index.js

@@ -34,7 +34,7 @@ import messagesPortuguese from './translations/pt';
 import messagesChinese from './translations/cn';
 import messagesSpanish from './translations/es';
 import messagesCroatian from './translations/hr';
-import messagesCzech from './translations/cz';
+import messagesCzech from './translations/cs';
 import messagesItalian from './translations/it';
 
 import './index.css';
@@ -58,7 +58,7 @@ const messages =
 	'zh' : messagesChinese,
 	'es' : messagesSpanish,
 	'hr' : messagesCroatian,
-	'cz' : messagesCzech,
+	'cs' : messagesCzech,
 	'it' : messagesItalian
 };