Declare global loaded_localizations

Fixes the error:

  src/app-localization.js:1108:9 - error TS2339: Property 'loaded_localizations' does not exist on type 'Window & typeof globalThis'.
  
  1108  window.loaded_localizations = function loaded_localizations(language, mapping) {
               ~~~~~~~~~~~~~~~~~~~~

src/globals.d.ts

@@ -444,6 +444,7 @@ interface Window {
 
 	// app-localization.js
 	available_languages: string[];
+	loaded_localizations: (language: string, mapping: Record<string, string>) => void; // JSONP callback in the localization files
 	// msgbox.js
 	showMessageBox: (options: MessageBoxOptions) => Promise<string>;
 	defaultMessageBoxTitle: string;