**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
v8::Locker locker(isolate());
  v8::HandleScope handle_scope(isolate());
  return is_checked_.Run(GetWrapper(), command_id);
}
bool Menu::IsCommandIdEnabled(int command_id) const {
  v8::Locker locker(isolate());
  v8::HandleScope handle_scope(isolate());
  return is_enabled_.Run(GetWrapper(), command_id);
}
bool Menu::IsCommandIdVisible(int command_id) const {
  v8::Locker locker(isolate());
  v8::HandleScope handle_scope(isolate());
  return is_visible_.Run(GetWrapper(), command_id);
}
bool Menu::ShouldCommandIdWorkWhenHidden(int command_id) const {
  v8::Locker locker(isolate());
  v8::HandleScope handle_scope(isolate());
  return works_when_hidden_.Run(GetWrapper(), command_id);
}
bool Menu::GetAcceleratorForCommandIdWithParams(
    int command_id,
    bool use_default_accelerator,
    ui::Accelerator* accelerator) const {
  v8::Locker locker(isolate());
  v8::HandleScope handle_scope(isolate());
  v8::Local<v8::Value> val =
      get_accelerator_.Run(GetWrapper(), command_id, use_default_accelerator);
  return mate::ConvertFromV8(isolate(), val, accelerator);
}
bool Menu::ShouldRegisterAcceleratorForCommandId(int command_id) const {