live2.nicovideo.jp request (or bug)

[artiction]

• I'm reporting a new site support request
• I've verified that I'm running youtube-dl version 2020.12.14
• I've checked that all provided URLs are alive and playable in a browser
• I've checked that none of provided URLs violate any copyrights
• I've searched the bugtracker for similar site support requests including closed ones

https://live2.nicovideo.jp/watch/lv329581687

Regarding u/big_bill_wilson's response to my question on how to download danmaku from live2.nicovideo.jp,
the site is clearly supported according to how he got the JSON data of the site, but I checked through the --list-extractors and found out that it wasn't, so I don't assume that this is a bug. Rather, I'm requesting for the site to be supported.

Also, I'm posting the script and my youtube-dl version cause why not.

youtube-dl -v --write-sub --all-subs https://live.nicovideo.jp/watch/lv328633290
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: ['-v', '--write-sub', '--all-subs', 'https://live.nicovideo.jp/watch/lv328633290']
[debug] Encodings: locale cp1252, fs mbcs, out cp437, pref cp1252
[debug] youtube-dl version 2021.01.08
[debug] Python version 3.4.4 (CPython) - Windows-10-10.0.18362
[debug] exe versions: none
[debug] Proxy map: {}
[generic] lv328633290: Requesting header
[redirect] Following redirect to https://live2.nicovideo.jp/watch/lv328633290
[generic] lv328633290: Requesting header
WARNING: Falling back on generic information extractor.
[generic] lv328633290: Downloading webpage
[generic] lv328633290: Extracting information
ERROR: Unsupported URL: https://live2.nicovideo.jp/watch/lv328633290
Traceback (most recent call last):
  File "C:\Users\dst\AppData\Roaming\Build archive\youtube-dl\ytdl-org\tmpe72mu9fe\build\youtube_dl\YoutubeDL.py", line 803, in wrapper
  File "C:\Users\dst\AppData\Roaming\Build archive\youtube-dl\ytdl-org\tmpe72mu9fe\build\youtube_dl\YoutubeDL.py", line 824, in __extract_info
  File "C:\Users\dst\AppData\Roaming\Build archive\youtube-dl\ytdl-org\tmpe72mu9fe\build\youtube_dl\extractor\common.py", line 532, in extract
  File "C:\Users\dst\AppData\Roaming\Build archive\youtube-dl\ytdl-org\tmpe72mu9fe\build\youtube_dl\extractor\generic.py", line 3467, in _real_extract
youtube_dl.utils.UnsupportedError: Unsupported URL: https://live2.nicovideo.jp/watch/lv328633290