Enable "Copy", "Expand All" and "Collapse All" to be focusable

[lornajane]

The buttons to copy/expand/collapse the response examples aren't buttons! As <span> tags, they can be clicked with a mouse but not with any other tools, such as keyboard or screenreader. This is part of #1279.

From the Accessibility tab in Firefox:

Clickable elements must be focusable and should have interactive semantics. Learn more

These could be more useful as <a> tags with the same onClick events attached.