Feature Request - Add option to enable adding serial number in video's titles

[RitamDey]

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Can a feature be added such that the video's index number in the playlist is added to the beginning of the video's title while downloading. For example: This playlist has numbered their videos serially. Some playlists don't do it! Can a feature be added so that if a user requests then the downloader just adds the index number before or after the video title

[dstftw]

https://github.com/rg3/youtube-dl#output-template