Ability to capture the `systemSettingsChanged` event under macOS

[gestern]

Is your feature request related to a problem? Please describe. I suggest adding support for systemSettingsChanged event when a user changes selects light or dark view. Currently only notification occurs when the accent color is changed (sel_systemColorSettingsChanged_):

Describe the solution you'd like I suggest adding an event interceptor for "systemSettingsChanged", similar to the earlier approach for "sel_systemColorSettingsChanged_". Something like this:

defaultCenter.addObserver(settingsDelegate, OS.sel_registerName("systemSettingsChanged:"), 
                OS.NSSystemColorsDidChangeNotification, null);

Describe alternatives you've considered N/A

Additional context The event should be intercepted in a similar way to SWT.Settings event:

display.addListener(SWT.Settings, event -> {
            //....
        });

[jukzi]

please provide a PR

[laeubi]

please provide a PR

You can just add the help wanted label no need for a generic comment as of course we always like getting PRs...