Lang Files can be generated by creating an extension of the file <code>LanguageProvider</code> class. From there you can add the translations in the <code>addTranslations</code> method, which you must override.
To add a translation, call the <code>LanguageProvider#add</code> method. This method takes the [[Internationalization/1.18|translation key]] and a string that is the displayname for the key.