Documentation+SQLStudio: Add manual page for SQL Studio

Author: https://github.com/dykatz
Commit: a79896bb44
Pull-request: https://github.com/SerenityOS/serenity/pull/13582
Reviewed-by: https://github.com/bgianfo
Reviewed-by: https://github.com/kleinesfilmroellchen
Reviewed-by: https://github.com/linusg

Userland/DevTools/SQLStudio/MainWidget.cpp

@@ -205,6 +205,9 @@ void MainWidget::initialize_menu(GUI::Window* window)
     edit_menu.add_action(*m_redo_action);
 
     auto& help_menu = window->add_menu("&Help");
+    help_menu.add_action(GUI::CommonActions::make_help_action([](auto&) {
+        Desktop::Launcher::open(URL::create_with_file_protocol("/usr/share/man/man1/SQLStudio.md"), "/bin/Help");
+    }));
     help_menu.add_action(GUI::CommonActions::make_about_action("SQL Studio", GUI::Icon::default_icon("app-sql-studio"), window));
 }