add web sync files and key events

src/app_events.cpp

@@ -21,6 +21,7 @@ std::string win32_clipboard_get_text();
 void webgl_pick_file(std::function<void(std::string)> callback);
 void webgl_pick_file_save(const std::string& path, 
     const std::string& name, std::function<void(bool)> callback);
+void webgl_sync();
 #endif