Accessibility: explain how to leave code blocks without tab key

[max-nextcloud]

As WCAG states

... if it requires more than unmodified arrow or tab keys or other standard exit methods, the user is advised of the method for moving focus away." (https://www.w3.org/WAI/WCAG21/Understanding/no-keyboard-trap.html) this technically meets requirements

But it would be ideal to add an aria-describedby on the code block pointing it to a description informing the user that the arrow keys can be used to move focus out of the code block, any additional recommendations @michaelnissenbaum?

Originally posted by @Pytal in #4520 (comment)

[max-nextcloud]

Maybe it would be helpful to have the esc key unfocus the editor. That would work everywhere - even in code blocks and allow the user to use other means of navigation such as arrow keys again.

[michaelnissenbaum]

The question here is, what would a user (whether visual or non-visual) expect here. I would suggest placing a small visual hint next to the editor to support all users. One option could be to use an info button that opens a tooltip when activated. If you only want to address non-visual users, you could also work with "aria-describedby," but you should only use the attribute with the allowed elements.