Add support for 1.5.0 additions to Media RSS

[andyusyd]

The feed in question, http://social.feeds.brightcove.com/v1/accounts/6234086667001/mrss/syndications/f8388980-a935-4ed7-9cec-b2cbbac5f3c4/feed
and https://social.feeds.brightcove.com/v1/accounts/4342645250001/mrss/syndications/40e05d1e-79f8-4752-9808-ba01e376a3cf/feed

When I run it through the Validator, it returns with this error 'Undefined item element:' for all elements that were added in MRSS version 1.5, such as, media:subTitle
https://www.rssboard.org/media-rss
Please help to review, thanks

[dontcallmedom]

I can confirm this isn't handled by the validator at the moment; quoting from the media-rss page, these are the changes in 1.5:

Added <media:community> element for adding community content like ratings, tags, etc.
Added <media:comments> element for adding user comments.
Added <media:embed> element for adding player-specific embed code.
Added <media:responses> element for adding media responses to a particular media object.
Added <media:backLinks> element for adding links pointing to a media object.
Added <media:status> element for maintaining the state of a feed -- whether the feed is still active, or it has been removed/blocked by the publisher.
Added <media:license> element for specifying the licensing information of a media object.
Added <media:price> element for specifying the pricing information of a media object.
Added <media:subTitle> element for specifying the subtitles of a media object.
Added <media:peerLink> element for specifying the P2P link to a media object.
Added <media:location> element for specifying various locations conforming to geoRSS.
Added <media:rights> element for specifying the rights information about a media object.
Added <media:scenes> element for including scene specific information from a media object.
Added option for allowing/denying sharing of a media object in <media:restriction> element.

https://github.com/w3c/feedvalidator/blob/master/src/feedvalidator/media.py is what would need to be updated