**Is your feature request related to a problem? Please describe.**

MenuItem labels are meant to be short. There's currently no place to elaborate/clarify them.

**Describe the solution you'd like**

`NSMenuItem` supports a [`toolTip`](https://developer.apple.com/documentation/appkit/nsmenuitem/1514848-tooltip?language=objc) property. Would be nice if Electron could expose this.

From what I could find, [GTK (Linux) does not have any way to set tooltip on menu items](https://developer.gnome.org/gtk3/stable/GtkMenuItem.html).

No idea about Windows.

**Describe alternatives you've considered**

None.

**Additional context**

No.
shell/browser/api/atom_api_menu.cc
: model_(new AtomMenuModel(this)) {
  InitWith(isolate, wrapper);
  model_->AddObserver(this);
}
Menu::~Menu() {
  if (model_) {
    model_->RemoveObserver(this);
  }
}
void Menu::AfterInit(v8::Isolate* isolate) {
  mate::Dictionary wrappable(isolate, GetWrapper());
  mate::Dictionary delegate;
  if (!wrappable.Get("delegate", &delegate))
    return;
  delegate.Get("isCommandIdChecked", &is_checked_);
  delegate.Get("isCommandIdEnabled", &is_enabled_);
  delegate.Get("isCommandIdVisible", &is_visible_);
  delegate.Get("shouldCommandIdWorkWhenHidden", &works_when_hidden_);
  delegate.Get("getAcceleratorForCommandId", &get_accelerator_);
  delegate.Get("shouldRegisterAcceleratorForCommandId",
               &should_register_accelerator_);
  delegate.Get("executeCommand", &execute_command_);
  delegate.Get("menuWillShow", &menu_will_show_);
}
bool Menu::IsCommandIdChecked(int command_id) const {