At the moment the reply count is labelled by the topic list's header
column, which is good — but we don't actually describe what the link
does, so it's a little ambiguous.
This adds an aria-label to describe the behavior "jump to first post" so
it will be read as:
"n replies, jump to first post"
This provides better coverage for link-to-link navigation because it
both describes the number and the function.
Kris
f9273ddcb7