Subtitle tests requests

[johnragon78]

Checklist

• [ x] I'm reporting a broken site support issue
• I've verified that I'm running youtube-dl version 2019.11.28
• I've checked that all provided URLs are alive and playable in a browser
• I've checked that all URLs and arguments with special characters are properly quoted or escaped
• [ x] I've searched the bugtracker for similar bug reports including closed ones
• [ x] I've read bugs section in FAQ

Verbose log

n/a


## Description

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Would prefer to add additional support for subtitle features on various websites. Enhanced tests for these cases would be appreciated. In particular, cnn, foxsports, khanacademy, espn buggy subtitle checks.