Non-visible buttons are still tabbable and read out by screenreaders

I've created an MR with a change for this. I've changed to use a hidden attribute rather than visually-hidden, but this is often overridden by a theme, so I've also added a display: none; inline style.

I've added the drupal cms a11y tag as well as wcag SC2.4.7 applies here as well. sighted keyboard users might get confused if on one tab no focus is visible. will manually test the MR over the weekend, but the proposed solution looks good from my perspective. and i've also set the priority back to normal.