add gui.load_document namespace extension table argument & pass app library from standard pages loader

src/logic/scripting/lua/libs/libgui.cpp

@@ -1111,6 +1111,16 @@ static int l_gui_load_document(lua::State* L) {
     );
     auto document = documentPtr.get();
     engine->getAssets()->store(std::move(documentPtr), alias);
+
+    // namespace extension
+    if (lua::istable(L, 4)) {
+        if (lua::get_from(L, "table", "merge")) {
+            lua::pushenv(L, *document->getEnvironment());
+            lua::pushvalue(L, 4);
+            lua::call(L, 2, 0);
+            lua::pop(L);
+        }
+    }
     scripting::on_ui_open(document, {args});
     return 0;
 }