Add a default first menu item implementation.

[furby-tm]

• Created a default first menu item implementation, which is better than a dummy because this presents a standard "About MyApp" and ability to quit the app, similar to the default first menu item that SwiftUI creates by default on macOS.

It looks like the following:

[stackotter]

Lgtm, just trying out locally before merging

[stackotter]

Thanks for PRing this! Great quality of life improvement