Add API endpoint to retrieve custom languages and complete language pack

include/WebApi_i18n.h

@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#pragma once
+
+#include <ESPAsyncWebServer.h>
+#include <TaskSchedulerDeclarations.h>
+
+class WebApiI18nClass {
+public:
+    void init(AsyncWebServer& server, Scheduler& scheduler);
+
+private:
+    void onI18nLanguages(AsyncWebServerRequest* request);
+    void onI18nLanguage(AsyncWebServerRequest* request);
+};