Feature: #89929 - Galician flag

See forge#89929


When adding a new language to a site or the system (sys_language) the Galician flag (ISO-639-1 Code "gl") is now available for selection.


A previous error, where the flag for Greenlandic was available (ISO Code "kl") under the "GL" shortcut, was resolved with this feature, as both flags now represent the proper ISO code.