Accessibility: cannot tab to arrow buttons on small view

[kburk1997]

Describe the bug
Repro steps:

1. Go to redocly demo
2. Shrink browser window until arrow button appears
3. Tab through page

Expected behavior
The up/down arrow buttons are focusable.

Actual behavior
The up/down arrow buttons are not focusable.

Additional context
I filed a keyboard accessibility issue before (#2283) - let me know if I should combine all accessibility issues I found.

Is there already a way to configure these buttons to be accessible?

[lornajane]

Thanks for logging these issues, we really appreciate it. No need to combine them, sharing what you spot works perfectly.