Add copy comment functionality to the torrent list's context menu

PR #19846.
Closes #18890.

src/webui/api/serialize/serialize_torrent.cpp

@@ -160,6 +160,7 @@ QVariantMap serialize(const BitTorrent::Torrent &torrent)
         {KEY_TORRENT_LAST_ACTIVITY_TIME, getLastActivityTime()},
         {KEY_TORRENT_AVAILABILITY, torrent.distributedCopies()},
         {KEY_TORRENT_REANNOUNCE, torrent.nextAnnounce()},
+        {KEY_TORRENT_COMMENT, torrent.comment()},
 
         {KEY_TORRENT_TOTAL_SIZE, torrent.totalSize()}
     };