Notifications should not steal focus if the user has interacted with the page

We now change focus to notifications on page load, but this can cause focus change when the user has already started to interact with the page.

I suspect that we need to change our rules around focus to be less greedy such that we only change focus if the document.activeElement is the document.body.

We may need to check if the screenreader changes the initial active element on page load, etc.