Add JS to update div outside of mustache

When the results have been loaded, JS now updates an aria-live region on the page with the result count. This means screen readers will read out the new result count.
Add a couple of tests for new aria updating
Add aria-hidden to mustache count

For screen readers the count appears outside of the mustache template so it is always on screen and always read out, so we can aria-hidden=true it here so it doesn't get read twice.