Add support for "game" & "title" to Twitch livestreams

[lextra2]

Checklist

• I'm reporting a feature request
• I've verified that I'm running youtube-dl version 2019.11.05
• I've searched the bugtracker for similar feature requests including closed ones

Description

Having support for retrieving the game category and stream title for twitch streams would be a very nice addition.

I know #22501 asked for almost the same thing but was closed under the assumption that twitch has no support for this in their API, which is wrong.

You can find more info on their API here

[tim-sorrels]

Hi, I would like to take a stab at adding support for this. So, similar to #22501 ,

youtube-dl --get-filename -o "title - %(title)s, game - %(game)s" https://www.twitch.tv/DansGaming
title - Dan is Batman? - Telltale's Batman, game - BATMAN - The Telltale Series

Where the title is "Dan is Batman? - Telltale's Batman" and the game is "BATMAN - The Telltale Series"

Is this the expected behavior?