Web/Push Notifications and Accessibility

I would like to know if there is any information or support available regarding Accessibility features with respect to Web Notifications on Chrome and Firefox browsers. We are trying to implement Web Notifications using the Notifications API https://notifications.spec.whatwg.org/ and are unable to use keyboard to get focus to the web notification in the bottom right. We can though access the Accept/Block popup that requests the permission to allow notifications when we use keyboard tab or spacebar. We believe it is a very important ability to support people with disabilities. Thanks in advance