Add option --netrc-cmd (#6682)

Authored by: NDagestad, pukkandan
Closes #1706

yt_dlp/options.py

@@ -720,6 +720,10 @@ def create_parser():
         '--netrc-location',
         dest='netrc_location', metavar='PATH',
         help='Location of .netrc authentication data; either the path or its containing directory. Defaults to ~/.netrc')
+    authentication.add_option(
+        '--netrc-cmd',
+        dest='netrc_cmd', metavar='NETRC_CMD',
+        help='Command to execute to get the credentials for an extractor.')
     authentication.add_option(
         '--video-password',
         dest='videopassword', metavar='PASSWORD',