Add Screenshots to Notifications section

## Problem

There are a number of visual consequences for using the various parts of notification API such as setting images, icons, urgency, replacing, etc. It might not be clear to developers which part of the API to use depending on their intended outcome

## Proposal

It would be helpful to add various screenshots and/or animated gifs to each section showing what it looks like to have, for example an urgent notification or setting an icon vs sending an image