add getSubChannel Name, Url and AvatarUrl for playlists

extractor/src/main/java/org/schabi/newpipe/extractor/playlist/PlaylistExtractor.java

@@ -6,6 +6,8 @@ import org.schabi.newpipe.extractor.exceptions.ParsingException;
 import org.schabi.newpipe.extractor.linkhandler.ListLinkHandler;
 import org.schabi.newpipe.extractor.stream.StreamInfoItem;
 
+import javax.annotation.Nonnull;
+
 public abstract class PlaylistExtractor extends ListExtractor<StreamInfoItem> {
 
     public PlaylistExtractor(StreamingService service, ListLinkHandler linkHandler) {
@@ -20,4 +22,9 @@ public abstract class PlaylistExtractor extends ListExtractor<StreamInfoItem> {
     public abstract String getUploaderAvatarUrl() throws ParsingException;
 
     public abstract long getStreamCount() throws ParsingException;
+
+    @Nonnull public abstract String getSubChannelName() throws ParsingException;
+    @Nonnull public abstract String getSubChannelUrl() throws ParsingException;
+    @Nonnull public abstract String getSubChannelAvatarUrl() throws ParsingException;
+
 }

extractor/src/main/java/org/schabi/newpipe/extractor/services/peertube/extractors/PeertubePlaylistExtractor.java

@@ -63,6 +63,24 @@ public class PeertubePlaylistExtractor extends PlaylistExtractor {
         return playlistInfo.getNumber("videosLength").longValue();
     }
 
+    @Nonnull
+    @Override
+    public String getSubChannelName() throws ParsingException {
+        return playlistInfo.getObject("videoChannel").getString("displayName");
+    }
+
+    @Nonnull
+    @Override
+    public String getSubChannelUrl() throws ParsingException {
+        return playlistInfo.getObject("videoChannel").getString("url");
+    }
+
+    @Nonnull
+    @Override
+    public String getSubChannelAvatarUrl() throws ParsingException {
+        return getBaseUrl() + playlistInfo.getObject("videoChannel").getObject("avatar").getString("path");
+    }
+
     @Nonnull
     @Override
     public InfoItemsPage<StreamInfoItem> getInitialPage() throws IOException, ExtractionException {

extractor/src/main/java/org/schabi/newpipe/extractor/services/soundcloud/extractors/SoundcloudPlaylistExtractor.java

@@ -114,6 +114,24 @@ public class SoundcloudPlaylistExtractor extends PlaylistExtractor {
         return playlist.getNumber("track_count", 0).longValue();
     }
 
+    @Nonnull
+    @Override
+    public String getSubChannelName() throws ParsingException {
+        return "";
+    }
+
+    @Nonnull
+    @Override
+    public String getSubChannelUrl() throws ParsingException {
+        return "";
+    }
+
+    @Nonnull
+    @Override
+    public String getSubChannelAvatarUrl() throws ParsingException {
+        return "";
+    }
+
     @Nonnull
     @Override
     public InfoItemsPage<StreamInfoItem> getInitialPage() throws IOException, ExtractionException {

extractor/src/main/java/org/schabi/newpipe/extractor/services/youtube/extractors/YoutubePlaylistExtractor.java

@@ -149,6 +149,24 @@ public class YoutubePlaylistExtractor extends PlaylistExtractor {
         }
     }
 
+    @Nonnull
+    @Override
+    public String getSubChannelName() throws ParsingException {
+        return "";
+    }
+
+    @Nonnull
+    @Override
+    public String getSubChannelUrl() throws ParsingException {
+        return "";
+    }
+
+    @Nonnull
+    @Override
+    public String getSubChannelAvatarUrl() throws ParsingException {
+        return "";
+    }
+
     @Nonnull
     @Override
     public InfoItemsPage<StreamInfoItem> getInitialPage() {