plugins.twitch: Add support for {title}, {author} and {category}
plugins.twitch: Add support for {title}, {author} and {category}

`streamlink --title "{title} - {author} - {category}" <url> best`

`{category}` and `{game}` both work interchangeably as per #1576

Title parsing works for live streams, VoDs and clips.

melmorabity/streamlink,bastimeyer/streamlink,beardypig/streamlink,melmorabity/streamlink,streamlink/streamlink,bastimeyer/streamlink,gravyboat/streamlink,chhe/streamlink,beardypig/streamlink,wlerin/streamlink,gravyboat/streamlink,wlerin/streamlink,chhe/streamlink,streamlink/streamlink