[Feature Request] download video description as txt file

[sl4vkek]

Hello developers,

I would like a new feature to be added to youtube-dl.
i want youtube-dl to have a --download-description option that would download the video's description as a txt file.
the txt file's name should be the same as the video file's name, except it ends with .txt.

[dstftw]

--write-description              Write video description to a .description
                                 file