This will likely end up being a game of whack-a-mole in the long run but
setting these headers seems to be sufficient to avoid getting a JS
challenge for now.

This is to fix an issue in Chromium browsers where they would offset the
page in a different direction to other browsers when the description was
show on hover, with a consequence being the cursor could be placed in a
way that would cause it to hover over the media image for one frame and
not for the next, resulting in a horrible flickering.

I think this new behaviour feels more natural, and allows users to go to
the linked media pages by clicking the description too, similar to how
it works on touch devices.

I was previously relying on the implicit `max-width` value set by
Tailwind's Preflight normalisation, which doesn't seem to be liked by
Firefox which appears to require a `width` to be set specifically.