Improve user interaction/contribution/ -> crowdsourcing

[user-A]

Hi, I like to submit the idea, that it might be wise, if gobblin gets more toward enable endusers to contribute to shared media. This can be for example:

• #800 split/mark periods in the mediastream and assist on identifying chapters
• #750 allow to contribute own translations of subtitles
• ...

I know that this will get complex and that there are some concerns, if a platform is that open (vandalism esp. spamming, ...). But IMHO if we allow the admin to manually change this settings, it would be a good feature, thats supports the creation of a community around a gobblin server :)