Add support for media source integration.

[niemyjski]

I'd love to have a picture or media card that could show a picture or video based on a path. I'd use this to show what mail is arriving today (/media/mail/mail_today.gif) or who last opened my mailbox (/media/mail/last_opened.jpg) as described here. This doesn't work with the current picture card because of authentication.

[FrnchFrgg]

I would very much welcome this: having lovelace send the required auth token from lovelace cards. Maybe by adding support for the media-source:// URI scheme (as already exists for service calls according to the documentation in https://www.home-assistant.io/integrations/media_source )