deduplicateYTPlaylist: support for URL without index parameter
deduplicateYTPlaylist: support for URL without index parameter

YouTube skips &index parameter if playlist starts from first item.
This fix detects such case and uses index=1, we additionally
build RegEx on the fly to match exact videoId (avoids any false-positives).

lidel/yt-looper,lidel/yt-looper,lidel/yt-looper