Why this change?
Prior to this change, we placed the identifier for the category using
CSS classes like `sidebar-section-link-<category slug>`. However, we found that it wasn't obvious
that an identifier for the category exists since it is first buried in
the CSS classes and second there isn't a way to describe what the
identifier is. Using data attributes, it makes it more obvious that an
identifier exists and what the identifier represents.
Alan Guo Xiang Tan
53eb49de72