Add a launcher start method and event to access the Window object

[AlexAPPi]

A new method and event should be added when the launcher starts so that the Window object can be accessed. At the moment, editor.call("launcher:start", launcher) is triggered here, but a clearer and more convenient API is needed to work with the opened window.

        const features = popup ? 'popup' : undefined;
        const launcher = window.open('', '_blank', features);
        if (launcher) {
            launcher.opener = null;
            launcher.location = url;
            editor.call("launcher:start", launcher); // Fire event
        }