**Add playlist metadata support to queue and events**

Enhanced queueing functionality to include playlist metadata, such as name, identifier, and track count. Updated event payloads to handle playlist information and introduced a new `playlist_added` event for streamlined notifications. Adjusted tests and documentation to reflect these changes.

src/main/java/me/bobert/netneutrality/music/SearchResultHandler.java

@@ -65,7 +65,8 @@ public class SearchResultHandler extends AbstractAudioLoadResultHandler {
         boolean truncated = tracks.size() > maxPlaylistSize;
         List<Track> candidates = truncated ? tracks.subList(0, maxPlaylistSize) : tracks;
 
-        String searchId = PendingSearchResults.put(guild.getId(), candidates);
+        String searchId = PendingSearchResults.put(guild.getId(), candidates,
+            new PlaylistInfo(identifier, result.getInfo().getName(), candidates.size()));
         future.complete(new PlayOutcome.PendingPlaylist(searchId, identifier, result.getInfo().getName(), candidates, truncated));
     }