All the review-related content on the review request page now supports

both light and dark modes. This includes reviews, change descriptions,

status updates, and replies.
There are some small color changes here and there, particularly to

replies and to status updates, to better align with the palettes and

provide better contrast. Change descriptions use diff theme colors for

all insert/delete indications.
The "Reply" and "Comment" links have been replaced with buttons, better

helping indicate that they trigger an action when clicked, rather than

taking the user to another page.

Tested on a variety of reviews, replies, changes, and status updates I

had locally.
This will of course need more real-world testing.