Support use of role for MenuItem

[scope2229]

If you use Electron MenuItem role option the error Uncaught TypeError: MenuItem must have at least one of label, role or type is thrown.

To reproduce inside the example instead of using the defaultMenu with TitleBar menu option use the following code

[
    {
      label: 'Menu',
      submenu: [
        {
          id: 'file',
          label: 'File',
          click: () => console.log("File"),
        },{
          role: "editMenu"
        }
      ],
    },
  ]

I think the role needs adding to the MenuItem type along with check the inside validate() not sure what else would be required though