Make the co-reviewer's avatars visible after they've accepted their invite

[murkatr]

Make the co-reviewer's avatars visible under Review Authors in the full PREreview section after they've accepted their invite. Similar to what we see above under Reviewers in the rapid PREreview section, we would like to see the avatars of the co-reviewers who accepted their full PREreview draft invites.

[dasaderi]

Without this it is impossible to know who has accepted the drafts. But also note that the multiple preprint authors publication seems to be broken issue #418