**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/ui/atom_menu_model.h
#ifndef SHELL_BROWSER_UI_ATOM_MENU_MODEL_H_
#define SHELL_BROWSER_UI_ATOM_MENU_MODEL_H_
#include <map>
#include "base/observer_list.h"
#include "base/observer_list_types.h"
#include "ui/base/models/simple_menu_model.h"
namespace electron {
class AtomMenuModel : public ui::SimpleMenuModel {
 public:
  class Delegate : public ui::SimpleMenuModel::Delegate {
   public:
    ~Delegate() override {}
    virtual bool GetAcceleratorForCommandIdWithParams(
        int command_id,
        bool use_default_accelerator,
        ui::Accelerator* accelerator) const = 0;
    virtual bool ShouldRegisterAcceleratorForCommandId(
        int command_id) const = 0;
    virtual bool ShouldCommandIdWorkWhenHidden(int command_id) const = 0;
   private:
    
    bool GetAcceleratorForCommandId(
        int command_id,
        ui::Accelerator* accelerator) const override;
  };
  class Observer : public base::CheckedObserver {
   public:
    ~Observer() override {}