Make jump buttons more keyboard accessible

[rebeccaalpert]

From IFD: “Back to bottom” button is sometimes unreachable via keyboard

• As the user tabs through the page, the “Back to bottom” button is often visible, but never reachable. By the time the user could tab to it, it’s gone.

Can access via rotor and scroll via keyboard. @thatblindgeye says users should be able to press Home or End key for the same effect if we wanted/needed a little more time to consider the keyboard focusability.

Popping this on the backlog as low priority for now since there are other workarounds.

[thatblindgeye]

This may still be worth looking into, as the to top/bottom buttons in the chatbot message container do more than just visually scroll to the top/bottom of the container; they also move focus, which Home and End keys don't do. So if I'm at the top of the container and press End then Tab, focus is still at the top of the container so I end up scrolling all the way back to the top anyway.