**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.h
public AtomMenuModel::Delegate,
             public AtomMenuModel::Observer {
 public:
  static mate::WrappableBase* New(mate::Arguments* args);
  static void BuildPrototype(v8::Isolate* isolate,
                             v8::Local<v8::FunctionTemplate> prototype);
#if defined(OS_MACOSX)
  
  static void SetApplicationMenu(Menu* menu);
  
  static void SendActionToFirstResponder(const std::string& action);
#endif
  AtomMenuModel* model() const { return model_.get(); }
 protected:
  Menu(v8::Isolate* isolate, v8::Local<v8::Object> wrapper);
  ~Menu() override;
  
  void AfterInit(v8::Isolate* isolate) override;
  
  bool IsCommandIdChecked(int command_id) const override;
  bool IsCommandIdEnabled(int command_id) const override;
  bool IsCommandIdVisible(int command_id) const override;
  bool ShouldCommandIdWorkWhenHidden(int command_id) const override;
  bool GetAcceleratorForCommandIdWithParams(
      int command_id,
      bool use_default_accelerator,
      ui::Accelerator* accelerator) const override;
  bool ShouldRegisterAcceleratorForCommandId(int command_id) const override;
  void ExecuteCommand(int command_id, int event_flags) override;