* Add new IEs
* Ant1NewsGrBaseIE: Base IE class
* Ant1NewsGrWatchIE: Extract videos from TV VOD pages
* Ant1NewsGrArticleIE: Extract videos from news articles
* Ant1NewsGrEmbedIE: Extract iframe-embeddable ant1news.gr videos
* NB: There is a different platform at vod.antenna.gr, which is not
covered here
* The Generic extractor can also be used to extract videos from news
article pages (through Ant1NewsGrEmbed._extract_urls), however a
specific IE is used to extract JSON-LD @type='NewsArticle' metadata
* However that does not work currently, as _json_ld does not support
@graph nesting
* Ant1NewsGrArticleIE defers to Ant1NewsGrEmbedIE, either as a playlist
or a single video
* Ant1NewsGrWatchIE and Ant1NewsGrEmbedIE query an API endpoint to
extract metadata, get the respective stream/source URLs and detect
video formats
* The endpoint HTTP path varies per IE
* Ant1NewsGrEmbedIE first resolves any redirects for its' own URL, to
derive the properl base URL for the API query
