Controller binding for tab for menu navigation

There are limited bindings for controllers. The bindings are defined here

Specifically, I wonder why these are bound:

case SDL_CONTROLLER_BUTTON_X:
                key = MyGUI::KeyCode::Semicolon;
                break;
            case SDL_CONTROLLER_BUTTON_Y:
                key = MyGUI::KeyCode::Apostrophe;
                break;
            case SDL_CONTROLLER_BUTTON_LEFTSHOULDER:
                key = MyGUI::KeyCode::Period;
                break;
            case SDL_CONTROLLER_BUTTON_RIGHTSHOULDER:
                key = MyGUI::KeyCode::Slash;
                break;

If possible, it would be nice to add Tab to this list, or replace one of these. I can't find these key codes anywhere else in the codebase. But I am probably missing something.

Keyboard navigation requires tab to be able to switch between buttons.

It is very simple to add here, so if this change is favorable, I will submit the MR.