Add locale data loading for extensions

public/scripts/i18n.js

@@ -11,6 +11,30 @@ var localeData;
 
 export const getCurrentLocale = () => localeFile;
 
+/**
+ * Adds additional localization data to the current locale file.
+ * @param {string} localeId Locale ID (e.g. 'fr-fr' or 'zh-cn')
+ * @param {Record<string, string>} data Localization data to add
+ */
+export function addLocaleData(localeId, data) {
+    if (!localeData) {
+        console.warn('Localization data not loaded yet. Additional data will not be added.');
+        return;
+    }
+
+    if (localeId !== localeFile) {
+        console.debug('Ignoring addLocaleData call for different locale', localeId);
+        return;
+    }
+
+    for (const [key, value] of Object.entries(data)) {
+        // Overrides for default locale data are not allowed
+        if (!Object.hasOwn(localeData, key)) {
+            localeData[key] = value;
+        }
+    }
+}
+
 /**
  * An observer that will check if any new i18n elements are added to the document
  * @type {MutationObserver}