Adds new DisableTimeout setting

[chrissainty]

Resolves #193

[Cvijo]

hi @chrissainty, I think you will need to add instanceToastSettings.DisableTimeout ??= DisableTimeout; to BuildCustomToastSetting too, i think it would be null if they don't set it on instance settings and this line Settings.DisableTimeout!.Value would throw error i think

    private ToastSettings BuildCustomToastSettings(Action<ToastSettings>? settings)
    {
        var instanceToastSettings = new ToastSettings();
        settings?.Invoke(instanceToastSettings);
        instanceToastSettings.DisableTimeout ??= DisableTimeout; **<-- this line**

        return instanceToastSettings;
    }

[chrissainty]

@Cvijo Great spot!