Create DEFAULT_LANGUAGE for whole bridgehead

[djuarezgf]

The teiler utilizes a multifrontend architecture integrated with internationalization, necessitating a default language setting. To ensure consistency, all forthcoming microfrontends should adhere to this default language. This standard should extend beyond the teiler to encompass other UIs not reliant on it. Presently, we've established a variable, TEILER_DEFAULT_LANGUAGE, exclusively for the teiler. However, given the influx of projects featuring UI components, it's prudent to anticipate this need now by implementing a global variable, DEFAULT_LANGUAGE, to govern the entire bridgehead. This proactive approach will mitigate the risk of potential misconfigurations within the bridgehead.