* Fixes the z-index of the prompt so it is behind the quick access panels
* Adds a dismiss `X` button (made sure the click target of this was quite big)
* Change structure of HTML to address template lint issues
* Fix aria-hidden not returning true/false
* Reload current page instead of navigating to / when clicking on the prompt message
This moves the "This site was just updated" modal asking the user if they want to refresh into a subtle prompt that slides down from the header.
Also in this PR I've added a helper to publish message bus messages in JS tests. So instead of this:
```javascript
// Mimic a messagebus message
MessageBus.callbacks
.filterBy("channel", "/global/asset-version")
.map((c) => c.func("somenewversion"));
```
We can have:
```javascript
publishToMessageBus("/global/asset-version", "somenewversion");
```
