Plugin Directory: single plugin view -- add indicator when reviews got a response

[jeherve]

Today, plugin authors are encouraged to reply to reviews, exchange with reviewers, and in many ways, the way a plugin author responds to a critical review is almost as important as the initial review itself.

As the new plugin directory features reviews on the single plugin page, I think it would be nice to add an indicator -- a link, a comment bubble -- next to the review title, when that review got a reply.

Here is an example:

[jeherve]

Preview of a review with a reply

[ocean90]

Duplicate of #1805.