[YoutubeDL] Add support for playlist_uploader and playlist_uploader_id in output template (closes #11427, #15018)

README.md

@@ -539,6 +539,8 @@ The basic usage is not to set any template arguments when downloading a single f
  - `playlist_index` (numeric): Index of the video in the playlist padded with leading zeros according to the total length of the playlist
  - `playlist_id` (string): Playlist identifier
  - `playlist_title` (string): Playlist title
+ - `playlist_uploader` (string): Full name of the playlist uploader
+ - `playlist_uploader_id` (string): Nickname or id of the playlist uploader
 
 Available for the video that belongs to some logical chapter or section:
 

youtube_dl/YoutubeDL.py

@@ -975,6 +975,8 @@ class YoutubeDL(object):
                     'playlist': playlist,
                     'playlist_id': ie_result.get('id'),
                     'playlist_title': ie_result.get('title'),
+                    'playlist_uploader': ie_result.get('uploader'),
+                    'playlist_uploader_id': ie_result.get('uploader_id'),
                     'playlist_index': i + playliststart,
                     'extractor': ie_result['extractor'],
                     'webpage_url': ie_result['webpage_url'],